I usually print on an Ultimaker 2+ and had endless problems with adhesion (glass plate). Especially with Extrudr Greentec filament. Since I’ve been using a Filaprint plate (FilaPrint® — Filafarm), this is history. On the contrary, I have to put the plate in the freezer from time to time to release the print.
I currently only print PLA on the A1M with PEI plate and have no problems.