Ender 3 Bowden tube popping off I keep having a recurring problem with my ender 3 pro.  The bowden tube keeps popping off here (pictured)

I've read elsewhere online where people are having a similar problem, i.e. the ptfe tube is actually popping out, but I don't know if thats the case here.  It's staying attached to the metal coupler, but that metal coupler is unscrewing during the course of the print and falling out.  Any tips to fix it?  New one? Some sort of loc-tite to get it to not unscrew?  Any ideas?
If the fitting is remaining attached to the PTFE tubing, that would indicate that the threaded end of the fitting is pulling out of the drive assembly. This implies that the internal threads of the drive assembly have stripped out. This is not unusual for a plastic drive assembly.
The best solution is to replace the drive assembly. I believe I paid about US$12 for the last one I purchased and it was aluminum, not plastic. A quick search for &quot;Ender 3 drive mechanism&quot; returned a number of choices. One of them from Amazon (14.98) is anodized aluminum and purports to be improved over the original.

A less than ideal solution would involve drilling out the stripped threads and installing an insert (sometimes called a Heli-coil™) but that could be as expensive as a replacement mechanism.