Would be interested to know who the manufacturers are of the different boxes? I have seen comments that the Samsung boxes are slower than the other manufacturer, which I think is Cisco, but I may be wrong. Mine is a Samsung and crawls at snail pace.
Have you tried the standard procedure of every 2 or 3 days,
Clear and reset thumbs and recommendations, even if you have them turned off.
Permanently clear all old recordings.
Clear the cache by pressing Home, Thumbs , Thumbs down, then pressing Play twice.
Then at least once per week turn the box off, leave 5 minutes and turn back on.
It may also help to minimise the number of series links?
I am not sure how much difference each of the above makes but I do them all and it keeps the box crawling on.
Had my visit from vm this morning they changed my faulty box and WOW what a difference big thank to Josh and to Michael Turrell the tech who came fantastic customer service from him overall ten out of ten