Sounds like you're using rotomill which makes a nice base.
I'd make sure you're staying above that. When it (rotomill) comes out (like if your lower edge of the blower catches it), it's not uncommon to come out in chunks a size that your augers aren't going to appreciate. Keep shear pins at the ready.
If your shoes your using to set blower height are not sliding over your surface cleanly and are digging in, consider pulling those out and installing some small tires on the outside of the blower in the same area. If it were a push blower, I'd recommend bicycle training tires (very thin) but for a 3PH, I'd go with tires the size you normally see on hand trucks (2-wheel dollies).