LED Plug-ins have an LED and a Resistor and they do like to breath, I mean not get too hot, and inside the dash it does get warmer than on the side of the vehicle.
The resistor is mostly the culprit but connections do vibrate loose, check the connections for all of the LED Plug-ins and plug the cluster back in and see if it helps.
Not sure but maybe you can take the Plug-ins apart and check the resistors, probably just a chip and subject to overheating.
Maybe you can check the LED outside the dash, clean it up and see what happens; worth a shot.
One more thing, voltage needs to be constant, LED have a very small working range and they need to stay in that range or they will go out. LEDs can dim some but again not much and not as much as an incandescent bulb.
Now the question arises, what about colored HD194s to light the dash.
Someone on this site posted some red bulbs but i do not know how things turned out.
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