So, I worked on my n°4 the 25th
I checked and rechecked the parts, trigger guard, collar, front screw, trigger, sear, forend, sear lugs, contact points see attachments. I read and read again the "fitting a forend article", applied your advises.
I disassembled re assembled many times, one thing was changing, the position of the trigger guard when I reassembled was not similar every time : I obtained this
Attachment 68247 or
Attachment 68248
At the last reassembling I knock the forend in place, slightly. Because one sentence got my attention
The trigger guard should not spring at the rear or front….., NO it shouldn’t!
And I got this result
Attachment 68249.
I tightened the screw that matched the turns with or without the collar. I put the bolt in place and...I got my 2PO.
I guess that the problem came from the fact that when I reassembled the forend I didn't set it correctly, because it's really tight fitted and I must knock it in place.
This morning, at the range, I was happy, the rifle is shooting straight, I still have the 2PO, and she has a great potential, 5 rounds in 1.35"*1" at 50 yards (the 200 yards range is closed for the time being).
Problem is solved.