The edit list support patch from https://bugs.webkit.org/show_bug.cgi?id=231019 was reverted in https://bugs.webkit.org/show_bug.cgi?id=244428. While that patch isn't landed again, we're growing the first buffer of an append near the begining of the stream to make it start from 0. This workaround uses a tolerance of 0.1s, and can cause problems on frames short enough to fit more than one time in the tolerance margin (eg: 3 frames at 30fps would fit, as well as 6 frames at 60fps). 

The process of growing the seconde frame that still fit in the tolerance is triggering the deletion of the first frame, which is usually a sync one. This sweeps other frames into the deletion and causes problems.