This can happen when both AutoLoad and AutoPreview are enabled. AutoLoad causes the loop to load and begin playing, as usual, but the browser’s AutoPreview option also causes the loop to play — at its original tempo, which may be different than BPM’s current tempo setting. The result is two loops playing at the same time, out of tempo with each other.

To avoid this, turn off AutoPreview when using AutoLoad while BPM is playing back.