I am also learning fast, a similar but a different machine:
Add to you technique
Vertical tap on bench to settle the grinds
Side tap after a light tamp to settle the edges. I would not tap after a heavy tamp, I also heavy tamp twice and check the tamper is level - the grinds are level - in the filter basket.
Then occasionally with my finger I press around the inside of the basket to check the evenness of the tamp.
I am using the restricted double shot technique - uses a lot of grinds but oh so creamy and sweet. *So The above my not quite apply but may help