I imagine that your right flipper coil is heating up to the point that it simply stops working. It works the next day because the coil has cooled down. Next time you play it and the flipper stops responding see how hot that right flipper coil is.

The three switches being activated when you press the flipper button are the opto for the lower flippers, then the opto for the upper flippers (no upper flippers so that opto not registering won’t affect gameplay but it will eventually cause a credit dot) then the end of stroke switch is triggered when the flipper bat moves up.

Test your end of stroke switches first since they are mechanical. Glass off, go to switch test and manually move each flipper bat to the up position to see if your EOS switches are working. If either EOS switch is not working lift the playfield and check for a broken wire connection on the EOS switch. Since only one switch is activating when you hit the right flipper I know your upper flipper opto and your right flipper EOS switch are not working.

While you are manually moving your flipper bats with your hands, do they move easily and smoothly? Pull up from the playfield on your flipper bats. How much “up and down” play is there? You should be able to move them up/down slightly. When is the last time the flipper mechs were rebuilt? If your flipper coil is overheating the plastic coil sleeve is probably damaged from the heat.

If you have a mechanical issue with the flipper mech the friction makes the coil work harder and as it heats up it struggles harder and harder to overcome that friction.

If it’s an opto issue clean your flipper optos and test the voltage being supplied to your flipper opto boards (12v)

To determine if your upper flipper opto not working is a problem with the board or a problem with your wiring simply swap the left and right flipper opto boards. If the problem follows the board it’s a board problem. If the problem remains the same it’s a wiring problem.

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The Pump House above has all the right info for you.

My Fish Tales has a metal piece of spring steel to spring the opto interrupt back after the flipper button is released, but I don't know if that's an aftermarket fix, or if the machine was sold with that.

Does your flipper button opto use a plastic flipper interrupt with no spring steel to push it back into position when the flipper button is released?

One thing I would mention is that the plastic flipper opto interrupts on the flipper buttons had a design flaw in the original plastic.

According to a service notice in StarTech journal back in the day, the plastic part would get too flexible, and not 'quite' activate the flipper, but actually be activating for a fraction of a second and cause the flipper coils to get warm... which leads us to what The Pump House says above.

I personally have had the original plastic opto interrupt seem 'spongy'. You would push the flipper button, and if you were very familiar with how fast the opto interrupt should snap back, you could notice that it was slow to bend back to a fully closed position.

I personally never had a pinball with warm coils due to this, but I definitely replaced the original plastic flipper button opto interrupt plastic with the newly made ones that use a different material, and that fixed my flipper problems.

Another something to check.