Is this happening on late waves, like 50 upwards?
I also get this glitch
Happens at every wave but gets worse the higher the stage. More units on the field = More delay and lag. Practically if you were to speed the game up at 2X then units would shake and delay the start. If the game was set to 3X then the delay either gets super long or doesn't start at all. This only happens before the battle starts.
I'm an Android player