So far we haven’t been able to reproduce the white scrollbars here. You said the problem is intermittent and that it happens for old compositions only. Have you noticed any other patterns? Could you attach one or more compositions that exhibit the problem? About how often does it happen for these compositions?
@alexmitchellmus, I’m marking this bug report closed since we haven’t been able to reproduce the problem, but if you’re still seeing it and can provide any more info, please let me know.