300 hours is not that much. You have maybe 50 or 60 landings over the span of several months? In a GA plane you could get that in 5 hours of pattern work.

But everyone gets in a rut of 'bad' landings. So many variables effect landings. I don't fly the 170, so I can't help there, but I know i'm the 145, the different variants feel a bit different in the flare. Plus, weight and balance and flap settings can change things up a lot. When i'm flying with FOs and they can't squeak out a good landing, I always ask where they are looking... 9 times out of 10 they are starting to look to close towards the approach end of the runway, instead of far down the runway. I can almost consistently get a nice smooth landing, but every once in a while I kind of slam it down for no apparent reason.