I had a guitar that kept going out of tune. Two minutes after tuning it, it would need to be tuned again. Finally I took it to an expert, a guy who built his own guitars, and he said the guitar was warped in such a way that it couldn’t be tuned at both ends. If you tuned it at the top, it would be out of tune at the bottom, and vice versa. A lot of things are shaped like that.