Got my bolt last week,after I put it in I did not like it as the bolt is now under sping pressure.Shot it today but put the old one back in after 10rds because if you bump the charging handle the bolt carrier will not be closed and can cause an out of battery fireing or it will not fire.I will have to do some testing with primed brass and see.
I tried both the original and new "spring'ed" bolt to see for myself. I do agree that if the charging handle is bumped, the BCG can be placed slightly out of battery... with
EITHER 
bolt assembly. I was able to press the trigger and the hammer fell on both assemblies when the bolt was out of battery. I didn't do bullet pull, primer strike test fires, but I would imagine the same results you recorded would occur with either bolt assembly. I did notice that if you tapped the charging handle forward, the BCG would move forward, reducing the gap to a couple of millimeters, or completely closed.
999, if you have already tested the original assembly and had negative results in having an out of battery firing situation, disregard the meandering thoughts below...
I tried a similar situation with my AR15. Charging handle moved back so that the BCG is out of battery slightly and was able to have the hammer fall. Not sure if this would result in an out of battery discharge, but it could be possible. The likelihood that the charging handle would be moved out of it's locked position and cause the BCG to be out of battery would be pretty rare... maybe with a really dirty weapon? I guess that's what the forward assist is for...
All this being said, there are only a couple of situations I could imagine that the BCG of the TAVOR could come slightly out of battery due to the charging handle being moved from the forward position.
The first by accident by bumping into something. I tried this on several surfaces and was able to get the charging to come off it's detent. This occurred when I was very close to a wall/corner and pushed forward when the charging handle came in contact with the object the charging handle was in contact with. One could also snag the charging handle onto clothing, but I wasn't able to do this.
The other scenario would be if one did a "pinch check" to check the chamber. One would need to ensure that the charging handle is released with enough force to lock it back into place or, one would have to tap the charging handle forward back into place. I found that when pulling the charging handle back far enough to check the chamber, releasing the charging handle from that position, there was enough force to lock the charging handle back into place and have the BCG fully forward. The bolt carrier is substantial in size and weight!
As the situation described by
999 happens with both new and old bolt assemblies, I'm going to stick with the new bolt assembly as this will eliminate the slam fire situation. If there is something I am missing, please inform me as I am no gunsmith...
