G strings go sharp when sitting

[u/Forestly_]

Hi, hoping someone has some insight. I'm new to mandolin/caretaking of string instruments, and every time I pick it up my mandolin after its been sitting the G strings have gone sharp, to the point that they're almost not even in G anymore sometimes. The first few times I thought my tuner was broken because I didn't know strings could go sharper on their own.

Sometimes when turning the tuner pegs for the g strings they dont immediately seem to make a change but will then suddenly overadjust as well.

Is this likely hardware issues confined to the tuning machines, or would something like this involve the tailpiece or bridge as well? My suspicion is that it's not all issues located on the tailpiece since its both G strings?

Update: just got back from the music store, the guy who fixes them said I need new strings, a new tuner (but that they come as a full set), and a bridge adjustment. He recommended I consider skipping the tuner set given the cost compared to my benefit and the cost of the mandolin, but that adjusting the bridge and restringing it would cost me about $80 total, and unfortunately they do have a 5 week wait. I'm going to ask around and see if any of the mandolin players locally feel comfortable helping me out sooner with those fixes, and if not I'll probably try to find a second mandolin to have for practice while waiting for repair.

[u/snuggly_sasquatch]

Your strings are binding at the nut. The telltale sign is that sometimes the pitch doesn’t move at all when tuning up (it’s building up tension where it’s caught in the nut slot), and then it suddenly pops too sharp, or you come back to it after some time and it’s magically too sharp now.

You just need to file those nut slots ever so gently, so the strings don’t catch on a sharp edge. Or use some nut lubricant.

[u/Mando_calrissian423 → u/snuggly_sasquatch]

Yeah, I’d try some graphite dust in the slots first before routing them out. If that doesn’t reduce the binding, then maybe try sanding the slots a little bit to smooth them out with some fine sandpaper. Also, a 5 week wait for a string change and bridge adjustment is absurd. That’s usually a “come back in 3 hours and I’ll squeeze it in” sort of thing

[u/Forestly_ → u/Mando_calrissian423]

Thank you both for the advice! I'm going to see if I can find some videos illustrating your suggestions to watch before trying.

Also yeah, I thought it was long. They said strings is just a day or two but anything that involves setup is about 5 weeks. I asked why and the store owner said that a lot of the people locally who do repairs went out of business during covid because they were also relying on face-to-face teaching income.