DS Lite Boots and Operates in Slow Motion

So I just bought a used DS Lite off Ebay. It takes about 6 seconds after flipping the switch to actually boot up and when it does, everything is in slow motion. The “DS Lite” graphic is slow and so are the sounds. There is also a painfully high pitched sound coming from the speakers. This seems like a super random issue to me and I don’t really know where to start looking. As far as my untrained eye can tell, things on the back looked fine. Tried with a different battery and the problem persists. Any ideas?