Hopefully stupid question but were you replacing the pen nibs? My screen has been solidly responsive for several years of heavy usage, but the fiber nibs do get worn down and need replacing every few weeks/months (by design) or the pen starts exhibiting this behaviour.

I have to admit I have also switched back to real paper for a lot of tasks but I still like the remarkable as an e-reader, and enjoy writing on it occasionally, so I wouldn't say it's a big regret.