Thx. I'll post log tomorrowHi,
It will be down to your x264 encoding settings where its trying to maintain a certain quality and therefore sometimes jumps outside of the desired bitrate.
please can you post a log, details can be found here @ https://obsproject.com/forum/threads/please-post-a-log-with-your-issue-heres-how.23074/
This will help us to see your settings and to help.