how do i fix jumping strings?

[myricacae]

When i am tuning the higher strings on my rover mandolin, the strings often get to a certain pitch, then jump up to a much higher one, often missing out the note i actually want to be on.. they usually do it when tuning down too. I think its a problem with the slots in the bridge and/or nut, where the strings have dug deeper into the wood, but im not sure how to fix it, especially without affecting the action/putting different strings at different heights by making the slots deeper

Thanks for suggestions, magpie

[MikeEdgerton]

The nut slots are too tight for the strings. It needs to be setup.

[myricacae]

What's a good diy way to achieve that?

[myricacae]

Is there a good DIY way to fix it? Sanding them slightly outwards?

[MikeEdgerton]

They need to be very slightly wider. You can also try lubricating them with ordinary graphite from a pencil. The string is binding.

[Phil Goodson]

I usually use a set of acetylene tip cleaners that can be purchased for less than $10 at many hardware stores. You find the cleaner wire that is the size of the nut slot and then use it to gently sand the slot WITHOUT pushing down on the bottom of the slot and therefore making it too deep. Works well for me.
You must be very gentle and careful not to do too much.

Here's an example.

[James Miller]

Took my Rover to Greif's Music Store to have them set it up & tune it. The fella there cut the nut down drastically from where it initially was, and adjusted the bridge for $22.

Later found out the OEM strings were sour when playing with others in the local clubhouse. Since replaced with D'Addarrio mediums and this made a significant difference in sound - more so on the base strings. The volume increased!