Help - Slight echo when speed / pitch increase

[nodaybut2day]

I've been speeding up audiobook files by approximately 115%. They are audio files exported from Quicktime movies. When I do this there is a slight kind of lag or echo on one of the channels. It sounds like the sound is coming from a basement. Does anyone have a workaround or fix? Changing the pitch makes no difference so far. Using Version 2.8.7 (2576) on a Mac, running Big Sur 11.5.1