Well, after a few tests, this is what I will do going forward: leave the machine to warm up without portafilter, and 4-5 minutes before making a shot I will lock in the portafilter to reduce the idle temperature to around 91-91.5 and more importantly the extraction temperature to around 92 (+-0.5), this is all in temperature setting 0.
Another option is to find a position (not too tight, not too loose) for the portafilter to be locked in the grouphead.
Strange thing is, I did not have any problems like this in the first weeks of use so something happened inside the machine but at least I am glad I could find a “fix” for it. Will come back with updates and readings from the thermometer after a few more tests.
Who knows, maybe it will help somebody that has problems with the stability and doesn’t have a thermometer and has the V2 of the Mara (as Lelit said when I spoke with them, the V2 has a new more “aggressive” software to get the machine warmer faster and I am guessing they do this by overheating it after start-up).