User defined envelope crashes Writer

Linux Mint 18.2 Sonya

I tried to create a user defined 9 x12 envelope, using document/insert/envelope. After I made the defined entries I created a new document. Fine so far. Then I wanted to move the addressee portion and went back to the format window. The Size drop down box was empty, but the width and height remained at 9x12. Every time I click on any field in the format window Writer crashes. Sometimes completely, with a recovery message when I restart. Other times with an error window and a recovery message. I’ve tried to recover the document, and I’ve discarded the recovery data. I’ve tried the reset button in the format window. Nothing works. I cannot create any envelopes, of any size, now.