I'm suffering with the same issue on my Nano SE M2 Plus with twin DVB-S2 tuners.

I was thinking of perhaps swapping my internal HDD, as it currently had a 750Gb 5400rpm inside, but I also have a 350Gb 7200rpm spare and to hand, so was perhaps thinking the speed of the drive could be the issue? Mostly recording and playing back FTA HD content.

Don't know if anyone has any thoughts on that, other than, stop being lazy, change it and let us know