On top of the bug detailed here, I noticed on my protagonist rogue that Reckless Assault will lose its purple activation glow and activation sound. To create the bug I had saved my game with Reckless Assault active, then upon reloading that save the bug occurred when I tried to deactivate and re-activate the skill. The skill bonuses and penalties still register in the combat log and on the character sheet. I made a save where the skill was not active before saving, reloaded, and the skill's activation and deactivation worked just fine sound-wise and graphic-wise.
I tried attaching the save file with the bug but for some reason I cannot. Do I need permission to upload or something? Love the game guys. Keep it up.
Edit:
Seems like the bug isn't exclustive to Reckless Assault. Same thing was recreated with with Edar and the skill Defender. It's possible that this extends to all modal skills.