Shows right dimensions and image but upon INSERT it becomes wrong size and addresses are shifted up and down. This used to work and old envelope form modified with new addresses will work. W10 Version 7.0.6 LO
I had this issue and isolated it to the printer (Canon TRS8520). The printer defaults to standard, letter-sized, portrait mode fed from the bottom tray and reports that back to LibreOffice, which then tries and fails to format the envelope in a way that you can just put an envelope in the paper tray and get it to print correctly.
My problem: Canon printer gets confused by the odd paper size and chokes. When it does print, it has to suck the upside-down envelope from the bottom tray and roll it over inside the printer to print it, wrinkling the envelope or twisting it. The TRS8520 has a rear feed that will not roll the envelope over, but it refuses to feed that way with the standard/default print settings in LibreOffice.
My solution was to go to the PRINTER tab on the envelope dialogue window, select the SETUP button to bring up the PRINTER SETUP dialogue window, then hit the PROPERTIES button. That brings up your printer-specific properties page. My printer has six pre-defined settings (standard, business letter, paper saver, photo printing, envelope, etc.). Even using the pre-set ‘envelope’ settings didn’t quite fix the problems, and (by default) it isn’t set to any specific envelope size - you have to pick one every time. That feature seems to confuse LibreOffice which will still choose the odd-sized format when I pick ‘envelope’ in the printer properties.
I got around those problems by editing the ‘envelope’ properties tabs to #10 envelope, rear feed and portrait mode (default was landscape and that wasn’t working with LibreOffice). I saved this as an additional configuration called LibreEnvelope. The only trick now is to choose that configuration first using PRINTER → SETUP → PROPERTIES (I have to do this each time I print an envelope), and then change the settings in the normal LibreWriter ENVELOPE dialog box/tabs if necessary (those settings are saved for every new envelope). Now, any envelope I create with NEW DOCUMENT (ENVELOPE window) formats correctly. So the only thing I have to do now is bring up the ENVELOPE dialog box and pick PRINTER → SETUP → PROPERTIES → LibreEnvelope.