Hello buddy.
Yes 3.1 channel should be 4096, I suspect it's dropping because the power level is too low. It's a touch noisy too at only 40 db.
3.0 channels power are on the low side but within spec, at least at the time you took the data.
The worrying thing is the post rs errors on your 3.0 downstream.
You need a bit of a tune up/levels adjusted perhaps that will eliminate the noise.
Either way it's not your equipment, it's up to virgin to fix it.