Baby chickens jumping excessively at fences

I just started using the pre-release on my 1.13 world, and I noticed that my baby chickens now jump constantly at fence blocks in an attempt to escape their enclosure, and some are actually getting out. This never happened before the pre-release for 1.14 (the jumping behaviour and the escaping). Nothing about their environment has changed from 1.13 to 1.14, but they are constantly jumping to escape now.