Noticed, that sometimes when I have stacks and go to another level, the stacks disappear.
Same when “extra life” passive is used, stacks disappear.
And sometimes … when they disappear, due to this bug or just for the lack of enemies … when I encounter an enemy, the stacks keeps continue from where they stopped.
Have 300 stacks, no enemy around, they disappear … find an enemy, kill it and I have 301 stacks instead of just 1.