Question: Frequency of truss rod adjustments?

I have a 5-string Stingray HH Through Neck. Love this bass! I bought it new about three years ago. My question has to do with the frequency of truss rod adjustments. With most other basses I had, I rarely, if ever had to tweak the truss rod.

The same went for this bass for the first couple of years. Like most electric basses, I could have it in the case for a few weeks and when I took it out, it was still almost dead-nuts in tune. The base lives in the (finished) basement of our home in the northeast.

About three months ago, when I took the bass out after some time, I noticed all strings were detuned a fair amount (maybe 1/2 step). Also the playing action was noticeably high. I checked the neck curvature, per the manual, and there was more bow in the neck than usual. I turned the truss rod 1/4 turn (90 degrees) tighter, and it improved things considerably. Despite being a bit puzzled by the sudden neck motion, the bass played well for the few rehearsals I had at that time.

The bass was then back in its case for a month or so and when I went to play it yesterday, the action has now dropped very low to the point of the strings buzzing. It looks like I am going to have to remove some of the additional tension I put in a few months ago. I figure a 45 degree loosening should do it.

Anyway, the questions for the community are:

1) The abrupt detune worries me a bit, especially since this is a through-neck bass, so if something moved, it was part of the instrument. i looked closely, and there are no signs of the fingerboard delaminating, a loose bridge, or other obvious issues.

2) The sudden neck motion is new to me. Is it normal for the necks on MusicMan’s to move a little more than normal? My neck is painted (and thus should provide an additional barrier to humidity migration), but having to tweak the neck twice in a few months is a bit worrisome, given that this something I normally never had to do, including on a 4-string MusicMan (with a bolt-on neck). I thought it might simply be the wood settling, since the instrument is relatively new.

I am at least glad that I now have to spin the truss rod back towards the original factory setting (rather than tightening it further), but any thoughts from others who have more experience would be most welcome. I have a studio session in a few weeks, and I definitely would like to have the bass settled in for that.

All thoughts would be most welcome. Thank you.

Jonny Bass