I own a Z18 and initially between software and extruders I had a lot of issues to start. Since 3.4 and the 12.1 version extruders I have had very little problems getting out good prints. Most of my problems now are how I set my paramaters for infill and speed for the build size.

First comment I would have is for you to get hold of the support side and get a replacement bellow system on it's way, removing it may be a temporary solution but not a permanent.

Why would you want to get the build chamber to 80C, recommended is 35C, you only want the chamber to be hot, around 95-100F not a sauna at 176F, you couldn't even touch the acrylic if it got that hot, and there probably is no ability to reach that temperature without the unit being on fire anyway.

The camera only works on large builds over 10", it comes in handy on a 60-90 hour print when you want to check the status while you are away. The camera only works on WiFi or Cat 5 connection, if you are connected via USB you will not see the camera.

Your filament jamming is partly because of how the rolls are stored as well as shipped, loose rolls will overlap the strands causing it to bind when unrolling. Storing partial rolls loose without retensioning the filament and securing it into the holes on the outer plate will allow the coil to loosen and again allow for overlapping strands causing binds.

The current UI is meant for the novice user, hence the limited options. Manually editing via a text editor is for the advanced user. I am accustomed to this as I also run several CNC machines and even with my high end milling programs I am constantly editing g code manually through a text editor. Since MB went to a proprietary control program to run its machines the only current way to modify the open parameters of your Z18 and all 5 Gen is via the text editor.

You have done a lot of work on this yourself but since it was bought by the school I would probably have suggested they requested a return of the Z18 for replacement if it came in that poor of condition. Depending on how the school directed you to service the unit "ie I don't care what it takes, get it running for the class" and your direction from support, you may have eliminated the ability to return the unit for replacement based on what you have said you have done to it. But that would be a discussion with the schools purchasing department and MB themselves.

My Z18 arrived firmly packed, no loose parts and everything looked pristine. The Drop tag was still charged as well as the "Do Not Stack" cone was still attached to the top. Again my issues were with the software and the extruders.

For suggestions on what you are trying to print post what it is either by picture of the model or a link if it is off Thingiverse or some other site and I will try to print it and give you the parameters that work for me. A good model design is just as important as the printer itself.