Maybe something is wrong with the script generating these test prints, if you don’t have any similar problems with normal prints?

In addition to the blobs in the middle of the circles, I think it looks overextruded/blobby every time it changes direction. E.g. if you look at the -20 sample, it looks generally underextruded as one would expect. Though it’s also blobby around the edges, where the lines make a U-turn. Since the printer usually slows down at turns (unless your acceleration is set insanely high) this could be an indication that you’re exceeding your hotends melting capacity, i.e. either temp is too low or speed is too high, so it would be interesting to know what you calibrated those values to. I don’t think this is usually associated with random blobbing in the middle of the print, but could be worth checking just in case.