this has been answered on discord so i'll post the results here:
issue happens with maps (some made by raaar) such as:
river of flame v4.1
highway 95 east v2
highway 95 west v2.1
(however it does not happens with highway 95 v5)
googlefrog successfully made a new test version of highway 95 east v2 without the micro stutters.
so i guess the issue has been identified.