I have not only restarted, I have reset. It doesn’t help.
We have had mixed responses here on this thread, some people are happy with kindle - and don’t forget I’m happy with kindle for reading “linear” texts: popular novels and journalism. My problem, like Sean’s, is when I try to use it for complex texts, where I need to flick around fast.
Anyway, it certainly could be a problem with my device, which is from 2017. Amazon have a deal where I can try another at no risk, free returns if it doesn’t live up to my expectations. I may just take them up on the offer.