I briefly had a Yamaha MSX machine (Z80? MS-DOS-like
disk format)
that I bought from Mitchell Waite. NO recollection of model number.
Its keyboard was a little flaky, and I never got around to disassembly
to check that out.
Probably CX-5M. You also have the CX-5MII and the CX-7M, but the worst
keyboard is on the CX-5M.
I love MSX :o)