Peter Wilson has provided another copy of his memfixa.sty, which patches memoir.cls. he writes:
I think that it does need another announcement as the person who tested the fix has distributed it to some others, so an announcement would make it official.
The fix now covers the memoir showtrims and oneside options and the calc
package.
i've installed the replacement file as macros/latex/contrib/supported/memoir/memfixa.sty
Robin Fairbairns
For the CTAN team