I tried the Looper presets for the first time today and ran into this too.
I was using the Basic Looper preset from the library and after recording a loop there were some very loud crackling sounds during playback, only in the right channel, and only during part of the recorded loop. I also couldn’t get it to overdub–the 1-Button Looper switch was not putting the looper into Dub mode. There were other strange things, like even while stopped I could not change the maximum record time. I came back later to try to figure it out and it was working normally. I couldn’t get it to happen again.
