Post a logfile of a recording session at least 30 seconds in length, and we'll be able to see if anything problematic is happening on the OBS side.
#1 most likely is if you're recording directly to MP4, which you should NEVER DO FOR ANY REASON. Record to MKV or FLV and remux to mp4 via the OBS File menu, Remux Recordings. Premiere tends to pitch a fit in a variety of interesting ways with obs native-record mp4 files, but the versions remuxed from flv/mkv work fine.