Exports from Premiere and Media Encoder creating bad files

Ever since the most recent premiere update, I've noticed problems with my exports. At random points during playback of the exported file, the video will freeze, get stuck, sometimes audio plays while the video freezes and sometimes everything is just frozen while the timeline ticks on until it unsticks seconds or minutes later. Always using a h.264 codec - haven't tested with others.

This happens with exports both from Premiere and Media Encoder.

Anyone else noticed this / any solutions? Super frustrating as the final files are often unusable. 

I've noticed sometimes it helps to re export but having to do this several times with each file is unacceptable.