Well ...
I have an older Icom hand held that has been very good to me but this sounds like the bean counters got into the design. Still they have a good reputation and this would be a good test of how they support their products - today! If you are like me (heaven forbid) you designed you instrument panel around specific hardware (avionics and instruments) and it would require an extreme problem that can't be worked around before you would change anything. That being the case, I would go back to the manufacturer and tell them exactly what happened (a photo would be good to start with) and see what their response is. Apollo was very good with the SL-60 problem. If they fix it free fine, if not I would bite the bullet and tell them to fix it anyway. It would be good to feed back the facts of you experience with the manufacturer in this forum when you have worked through the problem.
Once I got the unit back I would go to some length to minimize exposure of the unit to the sun. One of the options is to remove the unit from the rack until you are ready to test the systems and fly the airplane. When I built my plane Van had the upper fwd fuse skin truncated at the instrument panel but I extended it out about 4 inches to shade the panel. I bought a good avionics cooling fan to transfer the heat off into the passing air when the avionics are on. I installed an avionics master switch so the avionics are not sitting there cooking every time I turn the power on and forget to turn off all of the individual units. I also cut two round holes (maybe 3 in. dia) in the upper skin to vent the avionics. I cut two 1/2" ring doublers out of aluminum sheet and riveted them to the underside of the skin with some fairly fine mesh screen sandwiched in between to keep foriegn objects out. As a side benefit to the existence of these vent holes, I routed a defroster duct up to the left one for selectable windshield defrosting. I bought a canopy cover from Bruce's Custom Covers (I may have that name wrong but it's close enough to figure out) and cover the canopy when the plane is just going to be sitting out in the sun.
Bob Axsom