Another easy thing to check before disassembly - looking down at the top of the extruder, how well does the filament groove in the guidler bracket line up with the cut in the hobbed bolt? I know that on my printer, it took an unusual combination of a washer and R/C axle shims under the head of the hobbed bolt to get them lined up, and usarmyaircav has had a significant alignment problem with his. If the alignment isn't good, perhaps the filament moves around, sometimes riding on the deepest part of the hobbed bolt cut and other times riding on the shoulder of the cut. It seems like that could cause some extrusion variability.

Is the hobbed bolt free of any filament build up, as best you can tell?