M releases were temporary releases till the next version comes out. Consider them customer release used by more than one customer. It is totally not recommended to continue and run M versions after next version came out which means since r80.30 was released. Certainly not for such long periods (we are over a year from that time).
Moreover, since we started to release more frequent releases we are not releasing more M versions (we simply give ea instead).
There are 100’s of bug fixes in r80.20 and r80.30 jumbo’s that are all not part of r80.20m2 and they can cause all kind of issues.
We highly recommend to customers to upgrade to GA JUMBO of their respected release and in this case the jumbo for r80.20m2 is r80.30 ga jumbo
if you are using any M release, please plan your move from it to r80.30 or r80.40 (i think that r80.40 for management is a very safe choice by now regardless of your gw version)