Spirit Reserve stops working during weapon swap

Have a weapon swap system where swap 1 has minions reserved and swap 2 has zero reserved. Suddenly while mapping and swapping, Minions that were killed do not respawn. Reducing all minion counts to zero in the gem screen doesn't change the spirit reserve, and can no longer add minions back.

The bug fixed itself once I reinserted a spirit using gem, then it showed the correct spirit reserve.