First, read up on what midi notes/cc’s do within the sequencer.

Are you using OP1 as a controller? If so, you may be inadvertently sending an “Active track down A (69)” message.

I’m not too familiar with the OP1. Does it have polyphony settings?

Are you using the autochannel?

Have you loaded up the software for the ICM4+? It is pretty powerful and fairly well laid out for comprehension.