Hi! Thanks for your reply.
I have never known software to develop a bug unless the programmer has made changes to the code.
It worked for around 6 months with zero changes to code before first showing the issue (the machine that runs it is literally behind a wall so it was impossible for the code to be changed) . I then recompiled it and it went away for a few more months but now I seem to be stuck with it. This made me think it was nothing to do with the code. But then again, maybe some rare occurrence in the code causes the offset (and the code is messy as you say). Thing is, moving the image up would just leave blank/static pixels at the bottom? I wouldn’t even know how to wrap the image around they way it does if I tried.
In any case I will try using background method and generally tidy up the code and see if it still happens - thanks again for your help!