When the Denoise effect is applied on any clip in the timeline, any timeline operation (trimming clips, moving clips) may occasionally freeze the system for several minutes (causing the beachball on MacOS). The beachball always pulls through after several minutes of inactivity. When the filter is removed from the timeline, it seems to no longer cause this behaviour.

I have reset preferences, dumped media caches several times. This occurs on MacOS 10.13.6.