CiviCase- additional timeline- activity offset not working post upgrade

We've recently upgraded a site from 4.6.38 to 5.7

They were using cases with additional timelines. So they could add a new session to an existing case offset by 7 days from the "newest" activity of type x.

Post upgrade the additional timeline only offsets the new activity from the oldest activity of type x in the case. (This holds true wether the offfset is marked as oldest or newest in the timeline settings.

Just tested this out on dmaster.demo and found this works the same.