I had a Makala Concert and liked it, they’re generally unrecognised as a really good entry level instrument that could last someone for many years. IIRC there is no bushing in the headstock - so a single diameter hole through the headstock - and the tuning machInes are run-of-the-mill types that are sort of available on eBay for relatively little money. Unfortunately mounting (screw) hole centres are not standardised so you might struggle with that interchangability feature. I’d be inclined to lightly oil the shaft bearing surfaces before doing anything else. If you later remove one of the tuners you might both find a manufacturers mark on the underside and have chance to dissemble, fault find and rebuild to better operation.
