I'm on Slackware-15.0 here. I've an Ultimaker Mega X 300mm³ 3D Printer and have FINALLY set up to use the thing. I have a small little checker box which it prints. I've about a month's work lined up if everything worked perfectly … which it doesn't.

I tried to print this https://imgur.com/a/m02uqby as a testpiece. The width of those pieces is 208mm, and the height is 2x120mm which comes in under 280mm with the bars included. Here's the sad results.https://imgur.com/a/THR6yIG

The difference is that the first one has default settings, the second one is configured to print the parts individually. My guess is that it is not lifting the Z axis enough but kept printing. The top pic should show 4 parts but has no gaps. With the 'finish parts separately' option, You do see a division on the left for a bit.The little rectangular cutout just above it should be there, but the print is obviously displaced. I have NO EXPLANATION for the rectangles at the bottom right.

I'm using Prusa Slicer-2.4.2. I tried Ultimaker's Cura-5.0.0 and it starts, opens 3 processes, but never opens a file. The previous version was no better. The previous release of Cura didn't work either. I'm about to go off and install a windows version in wine or as a last resort windows 10 but they're having trouble there too. They say they are re-organising their build system. It was both an excuse, and a warning. It used to be that only they could build it. Now, apparently not even they can build it.

Any opinions, experience or advice welcome.

I think I have this.

The table is sprung loaded up, but adjusted down. I somehow managed to compress the back of it before zeroing it - and it stayed compressed; hence the mayhem. I've been setting tiny gaps in things as a Motorcycle mechanic for over half a century, but you still get the odd surprise.