Odd curling on flat printed surfaces

My Monoprice Maker Select 3D Printer curls up random bits of a flat surface that it prints (pictures show what I mean). It didn't do this before but I used slic3r, adjusted my height a bit because it wasn't printing the same, and now whatever I do makes it have different problems (such as having the prints look like the filament is crushed by having the plate too high or not sticking when the plate is too low). The curling doesn't actually usually ruin the print at all, more layers are printed over it and makes a fairly flat surface to print on, but the layers it messes up on look bad. I print with rafts and that makes it not have the problem on the build plate, but then when it prints the next flat layer for the actual print, it curls. Any recommendations for what I should do?

Your not extruding properly.
Check if all screws on the extruder are tight, especially the grub screw on the motor.
Check if the lenght you extrude matche what you measure with calipers.
Check the extrusion multiplier.
Do some test prints to check the above, like thin walled cubes, infill tests and some bridging.