Latency on external synth

I’m experiencing significant latency on my external synth when activating a MulitbandCompressor I’ve inserted on a different track. Bypassing the compressor doesn’t help, but when turning it off, the latency goes back to normal. I don’t see the connection. Anyone who does and can teach me a lesson?

My buffer size is either 256 or 384.

Could be Delay Compensation causing it.

Thanks! I thought of that but must admit I only have a vague idea what it is. The brief look I had at the manual yesterday didn’t help so I suppose I need to take a closer look.