I've done some analyzing. It is not the B-flat. It is the preceding G. It is a sequence of four 1/16-notes: G-flat, G, G, B-flat. The G seems to stay on forever. But more likely it is triggered to on and of by following G-notes. I have not yet figured out, exactly when it is turned off. When off, it is turned on by any played G during the first chorus. From the beginning of the first repetition (the second time through) the strange effect is gone.


Desktop; i7-2600k, 8 GB mem., Win 10 Pro, BIAB 2017; RB 2017 - latest build
Laptop: i5-2410M, 4 GB mem, Win 10 Pro, BIAB 2017; RB 2017 - latest build