PVR200T slow response to remote?

My Humax PVR200T has begun to respond to the remote control only after a delay of many seconds. It is sometimes necessary to reboot, and I have restored the default settings and gone through the procedure for setting the channels (manually) but these have not removed the delay behaviour. Remote has new batteries. Two years ago I cleaned the clock board.

I believe I am up to date with the software (version PGXTF 1.00.23).

Any help appreciated, thanks.