Sometime, I have the message "nable to teleport" and the the train move from auto to manual. I don't understand why. How can I take some log to help you ?
I have also sometime, when I try to put back my train, the message "STOP IT". I need to del my train to revover.

"unable to teleport" happens if there is something where the rolling stock is supposed to get spawned.
In most cases it is connected to snapping to the train stop, or a curved rail to near the exit depending on the trains speed. The latter can be avoided by having more straight rail to teleport to.

The "STOP IT" happens when parts of a train (subtrain) gets blocked and can't move at the speed the controlling train is. Since there is no way to check for collision I tried to guess about it by comparing the speed and see if there is a too rapid drop in speed. But it is a very unstable method probably causing lots of undesired side effects.

"unable to teleport" happens if there is something where the rolling stock is supposed to get spawned.
In most cases it is connected to snapping to the train stop, or a curved rail to near the exit depending on the trains speed. The latter can be avoided by having more straight rail to teleport to. -----
I don't think this is 100% true. I can put a strait rail with nothing on it for 100 pieces of rail and it'll still say "Unable to Teleport" I think there's a tick issue where if your UPS/FPS isn't high enough it can break the check and doesn't double check. Maybe having it re-attempt would be more beneficial. I do know it tries again but takes too long not to cause a train backup that the tunnel is attempting to avoid.