I have to confess that the A and D string gauge difference bit me the first time that I had the nut pop off. So, it is very likely my fault and I probably precipitated this following that mistake...
However, I widened the grooves prior to gluing the nut back on that first time. The nut stayed on just fine, until the next time that I changed strings (same gauge).
As I wrote, I've used CA glue again but this time putting it on the bottom as well as the fretboard-facing side of the nut. I put strings back on this morning, but have not fully tensioned them into tune... I'm trying to buy as many hours of cure time as possible before hitting the studio this morning. Fingers crossed that the stays in place!
The entire point of going back into the studio this morning was to re-record bass on a few tracks specifically for the Ric sound... the studio time was booked months ago. Argh! My GAS is saying, "You know what this means? We have to buy another Ric... you know, to have on-hand as a back up." 🤣