I still have the issue where MMS seems to just sometimes not work for days or even weeks on end, then suddenly start working again. No OS updates and no APN set

I still have the issue where MMS seems to just sometimes not work for days or even weeks on end, then suddenly start working again. No OS updates and no APN settings changes in the meantime. Normally it's not an issue, since I don't really use SMS all that much anymore, but my mother and I tend to send pictures back and forth a lot and she still uses SMS. SMS itself usually works fine, but MMS is particularly bad.