Digital Photo Professional 4 getting slower while working?

I use Digital Photo Professional 4 (Version 4.17.20.0) for my Canon R files, it starts slow yet acceptable, but when working it gets slower and slower and after 30 minutes it's impossible to work anymore.

I can't find a reason "slowness" increases over time.

Any ideia how to get it faster or at least it doesn't increase slow after some time working?

Thanks!