This is happening since some patch was released a few days ago.
After assigning a player to a new team using PlayerResource:SetCustomTeamAssignment() their heroes become completely invisible (like not having vision of them). As a temporary fix we added modifier_invisible and removed it again. Spells which apply modifier_invisible seem to make the hero completely invisible too (even for the owner). Without calling SetCustomTeamAssignment it works perfectly fine (though it crashes the game when ran like this in normal / non-tools mode). Besides my own mod (Warlock) some other mods seem to be affected by this too (Life in Arena).
I'll add more information soon when I find out more but maybe someone else knows something related.
After assigning a player to a new team using PlayerResource:SetCustomTeamAssignment() their heroes become completely invisible (like not having vision of them). As a temporary fix we added modifier_invisible and removed it again. Spells which apply modifier_invisible seem to make the hero completely invisible too (even for the owner). Without calling SetCustomTeamAssignment it works perfectly fine (though it crashes the game when ran like this in normal / non-tools mode). Besides my own mod (Warlock) some other mods seem to be affected by this too (Life in Arena).
I'll add more information soon when I find out more but maybe someone else knows something related.