Finally after approx 120 flights I had my first maintenance operations on my 620 SE yesterday... Funny thing is that three came the same day:
1)I was flying around when I heard "blink" and the tail boom support went loose (on the tail side) and dangled down near the blades (I was inverted). Flipped back upright, came back and landed. Put a screw back and went off to spool up
2)A small tracking issue. I was surprised as tracking was OK up to now. I adjusted the tracking and was of for second flight and third flight
3)At the end of third flight, the spool down was strange, the one way auto bearing seemed stuck. In fact that wasn't the problem, the pinion had come loose and slided down and engaged into the tail gear (I have the double stacked main gear, so I have a long pinion).
finally, I found what caused number 2. The "blink" from number 1 was in fact the screw fell onto the blade and slightly damaged it, that's likely why tracking went out.
There… after 8 months and 120 flight with 0 issues, I had two the same day, both related to screws coming unscrewed, I put them back with red loctite, should never happen again