Yamaha? Why did you buy that???

Just kidding, they make fine instruments. I know of some great players who play Yamaha… 😉

I would call the shop you bought it from and tell them ASAP. There may be a defect with it and it may need to be returned.

You could try a different valve oil. I have always loved “Al Cass” valve oil. I think it says “Fast” on the bottle, so mat be what you have. It’s clear.

And I would oil them at the start of your practice session, not the end.

My $.02 FWIW