Hey there, sorry about the problems. As far as the problems you are having, the Newer and older versions of the Creator pro all use the same parts in the print head.

It does sound like you have some things mucked up and a rebuild is needed. If you are stripping out blocks, that isn't anything new as the threading in the blocks isn't done very well. I have stripped out one or 2 myself. That's why I designed a better block.

On printer A to get the nozzle off you will need to heat it up and use a good set of pliers to grab onto the block and a 9mm wrench on the nozzle. It should come off with some good force.

I don't know what kind of budget your school has for the printers. But I have a supply of extruder mounts and all metal hot ends that makes maintenance way easier and the printer more reliable. I can give a nice "educational" discount too, PM for more info. On the all metal Microswiss setups I literally have many hundreds of hours of printing with no maintenance done. Being all metal, there is no PTFE liner to wear out.

Sometimes the PTFE liners aren't cut very well and are too short. This allows a little pocket to form at the bottom of the liner and filament can "coagulate" there and eventually plug things up. It just isn't a very good design overall.