It's usually the lubricants that cause the problems and need removing: they have either migrated from there there were meant to be, or they have gone hard or gu

It's usually the lubricants that cause the problems and need removing: they have either migrated from there there were meant to be, or they have gone hard or gummy. Care with solvents needs to be taken for their effect on non-metal parts. Many recommend alcohol, but it often contains a bit of water and doesn't easily dissolve oils and greases. I've found Sheelite (lighter fluid) to be about the best. For those of a certain age, Freon was the go-to solvent. Ozone layer be damned!