Deep Cleaning a Yamaha PF10!

Hi everyone - I recently bought a Yamaha PF10 for dirt cheap from an estate sale. Opened it up to see if I could fix a few dead/loose keys and ended up finding so much dirt and grime that I’ve decided to fully disassemble the thing and give it a deep cleaning, and hopefully learn a bit about how these things are built in the process.

The keys themselves are mostly plastic (and also FILTHY) so I was going to soak them overnight, but there’s a small piece inside that looks metal - anyone know what this is and whether the keys are safe to fully submerge or if there’s risk of this bit getting waterlogged/rusted? Or should I be fine if I just let them air-dry and then use compressed air to blow out the insides?

It looks like the pink stuff is the glue they use to hold in the small weight inside the key. If it feels sticky it is what hold the weight in place. If it is that happens when the unit is subjected to to much heat. It can drip out and get onto the contact board and may damage the rubber contacts as well. If it wasn’t stick before you applied hot water to it it is fine. Good luck!