Messed up the commit history, so here is all the files rip, Credit to TrinityCore

Source/Game/Entities/Player/Player.Fields.cs

@@ -122,6 +122,7 @@ namespace Game.Entities
         PetStable m_petStable;
         public List<PetAura> m_petAuras = new();
         uint m_temporaryUnsummonedPetNumber;
+        ReactStates? m_temporaryPetReactState;
         uint m_lastpetnumber;
 
         // Player summoning

Source/Game/Entities/Player/Player.Groups.cs

@@ -35,9 +35,9 @@ namespace Game.Entities
             return nearMembers[randTarget];
         }
 
-        public PartyResult CanUninviteFromGroup(ObjectGuid guidMember = default)
+        public PartyResult CanUninviteFromGroup(ObjectGuid guidMember, byte? partyIndex)
         {
-            Group grp = GetGroup();
+            Group grp = GetGroup(partyIndex);
             if (!grp)
                 return PartyResult.NotInGroup;
 
@@ -58,7 +58,7 @@ namespace Game.Entities
                     return PartyResult.PartyLfgBootDungeonComplete;
 
                 Player player = Global.ObjAccessor.FindConnectedPlayer(guidMember);
-                if (!player.m_lootRolls.Empty())
+                if (player != null && !player.m_lootRolls.Empty())
                     return PartyResult.PartyLfgBootLootRolls;
 
                 // @todo Should also be sent when anyone has recently left combat, with an aprox ~5 seconds timer.
@@ -150,6 +150,23 @@ namespace Game.Entities
 
             return false;
         }
+
+        public Group GetGroup(byte? partyIndex)
+        {
+            Group group = GetGroup();
+            if (!partyIndex.HasValue)
+                return group;
+
+            GroupCategory category = (GroupCategory)partyIndex;
+            if (group != null && group.GetGroupCategory() == category)
+                return group;
+
+            Group originalGroup = GetOriginalGroup();
+            if (originalGroup && originalGroup.GetGroupCategory() == category)
+                return originalGroup;
+
+            return null;
+        }
         
         public void SetGroup(Group group, byte subgroup = 0)
         {
@@ -167,10 +184,7 @@ namespace Game.Entities
         public void SetPartyType(GroupCategory category, GroupType type)
         {
             Cypher.Assert(category < GroupCategory.Max);
-            byte value = m_playerData.PartyType;
-            value &= (byte)~((byte)0xFF << ((byte)category * 4));
-            value |= (byte)((byte)type << ((byte)category * 4));
-            SetUpdateFieldValue(m_values.ModifyValue(m_playerData).ModifyValue(m_playerData.PartyType), value);
+            SetUpdateFieldValue(ref m_values.ModifyValue(m_playerData).ModifyValue(m_playerData.PartyType, (int)category), (byte)type);
         }
 
         public void ResetGroupUpdateSequenceIfNeeded(Group group)
@@ -207,12 +221,19 @@ namespace Game.Entities
         }
 
         public Group GetGroupInvite() { return m_groupInvite; }
+
         public void SetGroupInvite(Group group) { m_groupInvite = group; }
+
         public Group GetGroup() { return m_group.GetTarget(); }
+
         public GroupReference GetGroupRef() { return m_group; }
+
         public byte GetSubGroup() { return m_group.GetSubGroup(); }
+
         public GroupUpdateFlags GetGroupUpdateFlag() { return m_groupUpdateMask; }
+
         public void SetGroupUpdateFlag(GroupUpdateFlags flag) { m_groupUpdateMask |= flag; }
+
         public void RemoveGroupUpdateFlag(GroupUpdateFlags flag) { m_groupUpdateMask &= ~flag; }
 
         public Group GetOriginalGroup() { return m_originalGroup.GetTarget(); }

Source/Game/Entities/Player/Player.cs

@@ -109,8 +109,8 @@ namespace Game.Entities
             m_questObjectiveCriteriaMgr = new QuestObjectiveCriteriaManager(this);
             m_sceneMgr = new SceneMgr(this);
 
-            m_bgBattlegroundQueueID[0] = new BgBattlegroundQueueID_Rec();
-            m_bgBattlegroundQueueID[1] = new BgBattlegroundQueueID_Rec();
+            for (var i = 0; i < SharedConst.MaxPlayerBGQueues; ++i)
+                m_bgBattlegroundQueueID[i] = new BgBattlegroundQueueID_Rec();
 
             m_bgData = new BGData();
 
@@ -1057,6 +1057,55 @@ namespace Game.Entities
         public void SetLastPetNumber(uint petnumber) { m_lastpetnumber = petnumber; }
         public uint GetTemporaryUnsummonedPetNumber() { return m_temporaryUnsummonedPetNumber; }
         public void SetTemporaryUnsummonedPetNumber(uint petnumber) { m_temporaryUnsummonedPetNumber = petnumber; }
+
+        public ReactStates? GetTemporaryPetReactState() { return m_temporaryPetReactState; }
+        
+        public void DisablePetControlsOnMount(ReactStates reactState, CommandStates commandState)
+        {
+            Pet pet = GetPet();
+            if (pet == null)
+                return;
+
+            m_temporaryPetReactState = pet.GetReactState();
+            pet.SetReactState(reactState);
+            CharmInfo charmInfo = pet.GetCharmInfo();
+            if (charmInfo != null)
+                charmInfo.SetCommandState(commandState);
+
+            pet.GetMotionMaster().MoveFollow(this, SharedConst.PetFollowDist, pet.GetFollowAngle());
+
+            PetMode petMode = new();
+            petMode.PetGUID = pet.GetGUID();
+            petMode.ReactState = reactState;
+            petMode.CommandState = commandState;
+            petMode.Flag = 0;
+            SendPacket(petMode);
+        }
+
+        public void EnablePetControlsOnDismount()
+        {
+            Pet pet = GetPet();
+            if (pet != null)
+            {
+                PetMode petMode = new();
+                petMode.PetGUID = pet.GetGUID();
+                if (m_temporaryPetReactState.HasValue)
+                {
+                    petMode.ReactState = m_temporaryPetReactState.Value;
+                    pet.SetReactState(m_temporaryPetReactState.Value);
+                }
+
+                CharmInfo charmInfo = pet.GetCharmInfo();
+                if (charmInfo != null)
+                    petMode.CommandState = charmInfo.GetCommandState();
+
+                petMode.Flag = 0;
+                SendPacket(petMode);
+            }
+
+            m_temporaryPetReactState = null;
+        }
+
         public void UnsummonPetTemporaryIfAny()
         {
             Pet pet = GetPet();
@@ -1091,7 +1140,7 @@ namespace Game.Entities
 
         public bool IsPetNeedBeTemporaryUnsummoned()
         {
-            return !IsInWorld || !IsAlive() || IsMounted();
+            return !IsInWorld || !IsAlive() || HasUnitMovementFlag(MovementFlag.Flying) || HasExtraUnitMovementFlag2(MovementFlags3.AdvFlying);
         }
 
         public void SendRemoveControlBar()
@@ -6400,8 +6449,8 @@ namespace Game.Entities
         public void SendSellError(SellResult msg, Creature creature, ObjectGuid guid)
         {
             SellResponse sellResponse = new();
-            sellResponse.VendorGUID = (creature ? creature.GetGUID() : ObjectGuid.Empty);
-            sellResponse.ItemGUID = guid;
+            sellResponse.VendorGUID = creature ? creature.GetGUID() : ObjectGuid.Empty;
+            sellResponse.ItemGUIDs.Add(guid);
             sellResponse.Reason = msg;
             SendPacket(sellResponse);
         }