Something I didn’t see mentioned so far: have you checked if your nozzle is perhaps too old? I had filament curling upwards and creating blobs due to a nozzle being too old. Especially brass nozzles can wear out rather quickly if you use your printer regularly. If the filament would like to stick to the nozzle itself or move sideways (i.e. curling up when extruded) it rather quickly screws up prints.

Simplest way to check is of course to use other filament.