After creating or modifing a drawing and saving during the process I make the decision to PREVIEW and the PRINT. While in PREVIEW I verify everything and the change the SCALE to 1:2 and then PRINT. Close out of PREVIEW and return to the drawing. Before I exit I do a SAVE (already and existing drawing), and the software will only alow me to do a SAVE AS. Any time I save prior to changing the scale and printing it saves just fine.
This can happen, if the DXF file is somehow locked, e.g. by another software.
I have this sometimes, when the DXF is still open, while it is imported in OpenSCAD.
Then OpenSCAD locks the DXF and changes in LibreCAD can't be saved in the original DXF.
When saving fails in LibreCAD, it opens the Save as dialog to not lose any work.
I also remember issues, not in LibreCAD, but other office software, where saving failed when the file is located on a network drive. The consequence in LibreCAD would be Save as too.
So this has probably nothing to do with print preview or its settings.
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