I'm using Lightroom Classic CC. I print to an Epson 3880. I created a custom size paper 16 X 20. I select that paper in the page setup. When I return to the print screen the ruler only shows 8 1/2. When I click on the page setup again it defaults back to 8 1/2 x 11 paper.
I also tried printing in Photoshop CC had basically the same problem.
I printed on this paper about 6 months ago and did not have this issue.
Attached is a screen shot of the Lightroom CC screen showing the 16 X 20 is the paper while the ruler shows 8 1/2 as the size.
Try choosing a different printer, check paper size, then go back to the Epson. Sometimes the settings stick and chaning the printer resets it.
Try reinstalling the print driver, the profiles may have gotten corrupted.
I agree that something is off with the configuration and should be reset, but it isn’t clear exactly what. Reinstalling the Epson printer driver might help. I had a different problem with my Epson 3880 print settings earlier this week, and when I went to the Epson web site I found that there was a newer version of the Epson 3880 driver (version 10.9 dated December 2020) than I had. So I downloaded it and updated my Epson printer driver.
Another thing to try is to delete the file that contains user custom paper sizes, in case it became corrupted. Unfortunately I am on a Mac and from your screen shot it looks like you are on Windows; on my Mac I know that the file is called
and exists in
but I don’t know what the Windows equivalent of that is.
One last thing, when posting a screen shot, you might want to use a graphics format such as .jpeg or .png and post it inline using the Insert Picture button on the text editor toolbar, instead of as an attachment. The screen shot you attached is in .docx (Microsoft Word document) format, and when the forum software previews it, it displays distorted and important information is cut off along the right side (example below).
I tried this and found the same thing as you. I had to repeat the User Defined size on my Epson XP-15000 several times before it actually came back and reported everything correctly.
I had the same behavior of selecting User Defined only to find it was 8.5x11 when I went back in.
I suspect, there is some round-tripping between LrC and the Epson Print Driver that may be delayed.
I noticed that LrC seem to be confused if I also selected a Template. I had to select the User Defined setting in the XP-15000 in Page Setup.
I was able to get the ruler to show the correct width of 12.95 (max for the XP-15000)
You should start from scratch configuring everything, including of course Page Setup and paper size and make a new, virgin Print Template. Any better?