Try running them through Handbrake first before bringing them into Premiere.
That would add extra time and burden in rendering time as well as the output from handbrake would not be the original clip to edit
At least you get to edit without issues.
You are not the first to have problems with footage from a non widely used camera.
(PS I have also made a sub project with the earlier version of the premiere and imported the project into the current version which did not work.
Importing the rendered output clip from an older version of premiere into the current premiere version is similar to what you suggested doing it with handbrake
I have now 2-3 versions of the premiere in my pc which is not needed if the current version works properly