Thanks @chrisse. I tried the advice in the thread you found, but it didn’t make a difference. It took a while as it kept crashing while scrolling in the Settings app.
But since then a generous person sent me a spare core module they had and it’s all working again. I’m now thinking about how I can prevent this from happening again. If it’s because the GPU is overheating, does anyone know if it is possible to minimise GPU usage? I can disable the animation settings mentioned in the link in the post. But are there any other methods in Android to do this? I’ve had a look and I can’t find anything useful.
For reference, I managed to take a picture of the split screen issue I was having (below).