I'm experiencing spontaneous app crashes since upgrading to 12.1. It mainly happens in Mail but I've also experienced it in Safari and Photos. Anyone else seeing this?
I have not had any issues but I have a 2021 M1. If I had your issues I would start with running Onyx, an excellent free app that runs a bunch of maintenance apps. Select the maintenance tab and be sure to check the rebuild mailboxes in mail. If that does not fix the issues I would do a full install of Monterey 12.1.