MIMF

I have an old Banjo-Uke and the tuners won't keep the strings tight. I mean it's a matter of seconds and the strings go slack. Can I adjust the friction in the tuners or do I have to replace them? Here's a pic.

The screw that holds the button on is used to tighten them up. Give that a try first(if you have not already) Sometimes there are fiber washers that may be old and deteriorated. Nice looking Uke by the way.