That is surprising. I too am using PEI with Hatchbox (black & red) and PEI has been a miracle surface for me. My set up is as follows:
- Maghold aluminum Build plate. This shouldn't matter, just needs to be flat. I usually have it set to 60c
- PEI with 3M adhesive attached to build plate
- Hatchbox PLA. I use 190-200 to print.

I will say that you should make sure you are properly trammed, but it sounds like you are if you are successfully printing 20mm cubes.

Have you tried upping your bed temp a bit? I haven't had luck with anything lower than 50c on my CTC printer.

On a side note, I would love to try printbite. I currently can't justify it since my PEI is working so well, but it really sounds awesome from all the reviews.