No, it's not belts.
No, unlikely a nozzle.
Yes, probably an extruder or user failing to properly calibrate extrusion volume.
You say this:
I'm using a fresh reimport of the eSUN PLA+ open filament program settings with the same material. 0.4 nozzle installed and confirmed in settings
I read that as a massive failure of logic and reasoning. Yes, a profile is a good baseline, but regardless YOU have to print a test cube, you have to measure filament diameter, you have to put in the correct flowrate for even a different spool of the SAME plastic.
I'm trying to get this collective group up to a baseline of knowledge. Been trying for like 4 years.
If you have a problem, go back to basics.
#1 print the test cube 100% infill test.
https://forum.raise3d.com/viewtopic.php ... fish#p2620# Being how shiny that print is, you might be extruding a bit on the hot side of the equation and worse, that could be then causing issues with extruder further into the print failing to extrude the comanded volume of PLA due to heat creep or other issues. In a nutshell, here's what happens. PLA softens at a relatively low temperature well below the melting point. It's important to know this critical temperature. Point being, the extruder feeder has to grip the filament wire and push it into the nozzle with force to create pressure. Because the feeder is at the top and the nozzle is far down below on these printers, there is a long distance of filament being pushed. If that filament is hard and rigid, it pushes easily through the guide tubes inside the extruder head down the path to the nozzle and transmits that pushing force. If however, the block and path and the heatsink of the cold end of the extruder, along with the motor and feeder parts above and that PLA gets even slightly soft, now it's much harder to grip and push. End result is LESS filament than commanded. Let's not instantly jump to the assumption that is the root cause of the problem because I see a potential flaw in the use case where you and many other users have this concept of I just choose a given filament profile and it should be fine with NO OTHER calibration or adjustments, and that's "the problem".
So again, step 1 is ensure your settings and calibration are correct on a test cube. THEN reprint the part. Then if that fails, then go down the rabit hole of what if failures to extrude the commanded volume.