Hi,
I'm on a NB with Soulcleaver set with sorc subclassing to get Overload.
After activating overload and ulti has been fully consumed, it usually turns overload off so ulti starts filling up again.
When wearing Soulcleaver set, there seems to be a small random chance (not very often, happens ~1-2 times per loop in IA) that instead ulti is stuck at 0 and not filling up at all, until overload is manually deactivated. When ulti is stuck at 0, light and heavy attacks are impossible, no animation and no damage caused.

It's not a big problem but a little annoying especially when you don't realize immediately