Issue while Issuing donation receipt (SYSTOPIA Donation Receipts Extension)

Using donation receipt SYSTOPIA Donation Receipts Extension, issuing donation receipt creates this error (and does not complete)

Box property calculation requires containing block width

I’m running 5.31.0 on WordPress 5.6
I know your extension is not primarily intended for WordPress, yet in our set-up it used to run smoothly.. I guess this is due to 2.0 upgrade? Do you think I could revert to 1.8 or will this crash the DB?
Thanks!