RGB-modded SNES Jr. hardware issue - color artifacts

[ShutokouBattle]

I have this SNES Jr., which is RGB modded. It was modded years ago and was working perfectly until recently. Recently it began having this issue which seems to be a type of image artifact that alters the colors of certain parts of the image, which usually flicker somewhat. It usually appears pink or purplish. Often it only seems to affect one specific part of the image - like one sprite or a background. It seems like the commonality between the instances I've seen might be that it mainly affects transparencies, but I'm not totally sure about that. It seems to affect most games, but I've found a couple (Super Mario World and Kirby's Dream Land 3) that don't seem to show the issue at all. The effect seems to be related to the amount of time the system has been powered on in a particular instance, although the amount of time isn't always exactly the same. In general, it seems like it doesn't have the issue at first, but after 30 minutes to an hour of use, it appears. I've confirmed that the issue is almost certainly caused by the system itself and not any other equipment, as I've tested it with multiple video cables, power adapters, and monitors. The issue is the same in every case. Apart from the image artifact itself, nothing else about the games seems to be affected and the games run normally. Here are some images that show what I'm talking about.







Let me know if you have issues seeing the images, and I'll try to fix it. I can also provide higher resolution images, ones without the red boxes, etc. I could also take a video, if that helps.

The areas with red boxes around them are the artifact I mentioned. I've started using F-Zero as a frame of reference, since the way it appears in this game seems to be very predictable. I don't know exactly what caused this issue, but I have a theory: I was having another issue with this system (that I was ultimately able to fix), and in the process of troubleshooting that issue I think I may have damaged part of the system. I'm using SCART for output, and I believed that the issue I was having might be related to the power output (pin 8 on SCART) of the system. I connected a multimeter to the SCART connector in order to test the power output of that pin, and retrospectively I think I might have accidentally touched one of the other pins, sending power somewhere it's not supposed to go. This might've caused something to short out, or a component to be damaged or altered in some way. My guess would be it's something related to the video components in the system, since I was testing the video output and the issue seems video related. I don't know for sure that this is what caused the issue, but it seems likely. I never saw this issue before I did that, and it appeared very soon afterwards. It is possible that the issue might be related to the RGB mod, but if that's true then I think that something recently must've triggered it, since it didn't have this issue for years after it was originally modded.

So, I'm posting about this because I want advice about what I should do with the system. If I knew exactly what was causing the issue, I might be able to fix it myself. However, since I may have already damaged it once trying to do exactly that, I'm a little worried I might damage it again if I try to do it myself. So, what are my options? If I want someone else to fix it, who/where should I ask? Anyone who does this repair needs to have a way to test the RGB output of the system, since this is what I'll be using. What should I do? The way the issue appears seems fairly limited and very predictable - which makes it seem like it could be fairly simple to fix. The fact that it is so predictable should make testing easy - it should be easy to tell if any repairs solve the issue or not. So, what do you think?