Are there other users with the same problem?
Having problems with samples at the moment. Many installed samples packs on the OP-Z (from OP1 fun) have clicks and pops. And these just sounded good with a older firmware 1.2.38. All sample packs that you install via the app are just fine. So it has to do with the content mode. I also installed the firmware 1.240 and then copied all samples again. But problem remains. It’s not with every sound but often with kicks and low frequency sounds.
Resetting the device will not work.
I just downgraded the OP-Z to firmware 1.2.38 and restored all custom samples. Works like a charm again 
Was afraid for a hardware error.