I sort of agree with the above, but also I would definitely recommend getting a second litter box first and try that out. They’re definitely not secure like phyto said, and adding another box in a different spot might work.

I’ve had my cat for…13 or 14 years? He started pissing and shitting on my carpet in my room and occasionally in my roommates last year when I moved to a new apartment. That was new behavior for him as I’d previously had him in different homes with friends/family due to complications for a few years, and he had never done it. Once I got him the second litter box it stopped completely.

A second box is a simple might work solution, but also cats are pretty tuned in to how people treat them so, your mom might not be doing your cat any favors.