Client CPU usage

I run Roon core on a Mac Mini. I’m finding that the CPU usage of the client Roon on an iMac creeps up over time, even if I don’t use it. The iMac does sleep a lot, and I wonder whether this has anything to do with it. I just find Roon using a good 50% of a core and sometimes itself becomes very sluggish until I restart it. Any ideas?