This is a known bug that was in Firefox 82.0, but 82.0.1 should have prevented this happening if, and ONLY if, it hadn't already happened in 82.0. I'm guessing that you already printed using 82.0 before the update to 82.0.1/82.0.2, but maybe hadn't notice that?

If you open the page `about:config` and type in "print_paper", you should see a bunch of printer settings for your printer saved there. Try deleting all those settings for the affected printer(s) and see if that fixes things for you.

Also, I think this should only have happened if you set the "print_paper_width" and "print_paper_height" values to -1. Do you know if you ever set them to that?

Jonathan Watt thanks for the reply. I seen this with version 82.02 from most users. So i have downgraded to 81.0 and stopped automatic update. The only thing i changed on `about:config` is the "print.save_print_settings" to false. But the "print_paper_width" and "print_paper_height" are set to -1 as per attached picture, what should the values?

You will see the problem in 82.0.2 unless you delete the "print_paper_*" settings as I mentioned above.

You can set "print_paper_width" and "print_paper_height" (back) to -1 rather than deleting them if you like. If they are set to -1, then Firefox should use the paper size defined in the operating system's printer settings. If you delete them, Firefox will do the same, but then update the "print_paper_width" and "print_paper_height" values with the dimensions that came from the operating system the next time you print. The difference is that if they're set to -1, Firefox will check the operating system settings every time you print, which may be slower. The only reason you might choose to use -1 is if you like to change the operating system settings frequently and want to have Firefox pick up those updated settings whenever you change them.

I have deleted the "print_paper_*" for the printer still changing back to 'Letter' when i choose ‘Postscript Custom Page Size’ but if I use the preset paper forms like A4 it not reverting to letter.

What dimensions is the 'Postscript Custom Page Size' paper size configured to?

The dimensions set is Width: 11.50", Height: 8.50" and Paper Feed Direction is 'Short Edge First'

Interesting, so half an inch longer than US Letter. Maybe we have a rounding error of some sort since it seems unlikely that that size specifically would otherwise coincidentally be the size that reverts to US Letter.

After the size has reset, what values do the "print_paper_*" prefs in `about:config` have? (Particularly "print_paper_id")?

print_paper_id is 32767

I think we probably need to dig deeper here. Can you create an account on https://bugzilla.mozilla.org/ and report this issue there for investigation by the developers?

Jonathan, thanks for you time.

No problem. Did you file a bugzilla bug? If so, I can't find it - can you provide the link here? If not, and if you're having trouble with filing a bugzilla bug we can continue the discussion here. It will just be a bit more cumbersome.

I have just filled a bugzilla bug 1675694