I’ve used my 1986 QX5 MIDI sequencer for a project and it was quite challenging because the pushbuttons were unreliable, taking many button presses to get one to register, as well as sometimes bouncing.
The Internet told me that the buttons are tactile switches and I figured I could easily replace them. YouTuber “Unrelated Activities” measured the switch dimensions and found a specific replacement that’s not available to me, but the dimensions were very handy. Searching Amazon for 12mm tactile switch got me what looked like a close-enough replacement, with the 7.3-mm height from base of switch to tip of stem, allowing me to order the switches in advance and open the sequencer once instead of opening it and waiting for delivery.