can it really be an out of tune due to temperature ?
i really doubt that. I image when that happens each note gets some offset, but i'm getting really weird behavior that each time i press the same key it has a different tuning.. at the end it sounds like a pattern . not totally random.
It happend today 5 times within 2 hours.
I deleted now the calibration data and rerun the calibration. Let's see how it goes.
The T5 round robins through the 5 voices when played in poly mode. So if the voices are out of tune, you'll hear a repeating cycle every 5 notes, it's not random. If you put it in unison mode, you'll just hear voice 1 (or voices 1+2, 1+2+3 etc. depending on how many voices you set unison to).
Now that you've cleared the calibration tables, run a calibration anytime you hear the synth is out of tune and it should get more stable over time. Depending on where you reside, it's probably spring (or fall) and the weather is all over the place, gradually getting warmer so keep the calibrations coming.
Oh... check the vintage knob setting too. If it's cranked up (and it's saved per patch), the voices, filter cutoffs, envelopes, will all vary per voice. Set vintage all the way counterclockwise before verifying tuning.