I bit late on a follow up, but a couple of days ago I was manually shredding some bank account statements with some scissors I found lying around on the desk. The handle broke in the process and I did sufficient damage to my hand to keep me out of any somewhat heavy manual labor. Yesterday I finally got the job done.
OK, so heat and torque did it, without a problem. Seems they filled up the connector with the glue gun prior to closing, so heat was a must obviously, I doubt the thread locker was to blame in the first place.
Everything is working now.
...since this is likely a medical instrument and for such clean microbial environment is not going to be acceptable, let the institution pay for the new connector.
I'm the institution, well I am the owner now. It's a part of the imaging subsystem (microscope with a camera, control box), of a lot bigger device that is EoL, that I'd like to rework for my desk use for inspection and soldering. I will have to have some holder made and if this connector proved troublesome I would have given up since I would be approaching the cost of some simple commercial solutions..