just turned of phd2 and the speed of kstar is back to normal again. so fairly confident it is the link between phd2 and kstar causing the problem.
on the rpi4, which is where the phd2 is running on, things are smooth and responsive. so i donot think the rpi/phd 2 is the problem.
also just to reiterate, the it gets slow progressively, i.e. after restarting kstar, things will run smoothly for a couple of hours before grinding to a hault.