If session frame range selects cut length and cut in/out fields are blank, RV need to be restart to be used.
Here is the way to hack shotgrid_review_app.mu to force RV fall back to full frame range.
Note: The code will load media and set to full frame range. It won’t modify menu selection to Full Length. The fall back can be found in RV console.
The above code is a little bit different than default code. The modification is based on the changes of
Add new menu under Frame Range in ShotGrid Review App
If you just want to change cut length from default code, this can be followed.