All conditions involving ‘Players in Slot’ will stop working after changing slots within a team. The pointer is lost, and will neither point to the new player in the specified slot nor the player previously in that slot.
This will cause any game mode using ‘Players In Slot’ in conditions to break if the host swaps slots on players within a team.
Demo with workaround: X6GS5
EDIT:
The demo now has code for detecting and correcting the bug. To use it, paste all RENEW POINTER rules (FFA or TEAMS depending on your mode) into your game mode. The code will renew lost pointers every 5 sec globally. The players having their pointers renewed will respawn.
The RENEW POINTER rules might seem unintutive, but they do the job.