I’ve tried new and old PLA with little difference, the dimensions are always wrong. I put it down to the printer I used having zip-tied linear bearings (that can’t be good). It’s humid here, sub-tropical. I use one of those big moisture absorbers(buy them at woolies) to keep the PLA OK.
The strange part for me is if I print a calibration cube it’s perfect, but holes are just way off. I’ve tried different combinations of slicers and settings with no luck. Once again, Zip tied linear bearings? Printrbot shouldn’t have sold this kit – it’s more frustrating than it is enjoyable.