I've encountered the exact problem you describe, but without any consistency. It was different between identical roku boxes. One was fine, next box had repeats. Happened on different apps. The only common element was URC remotes with MRF boxes.
The solution was to alter the ir repeats in the macro window in ccp
I'm Not an engineer, but I play one on TV. My handle is Tweety but I have nothing to do with the organization of similar name. I just had a really big head as a child so folks called me tweety bird.