I have the S1 plus. I’ve upgraded everything from the bed to the extruder.

The biggest benefit I’ve seen is from removing the stock software and using klipper. It’s a lot to setup and calibrate, but it works well.

It sounds like you’ve done it perfectly. I’d suggest trying a different heatblock, but I doubt that would make a difference. Make sure they are all aligned in your extruder with no obstruction when you look through end to end.

I’ve had to do some heating and cleaning of my heatblock and heatbreak when replacing parts to remove bits of plastic. (Gentle wire brush and a burner lighter).

The only other thing that comes to mind is your thermistor or heatblock cartridge being damaged and reporting the wrong temperature. Temps too high or too low can lead to clogging.

If I were you and I had tried all these things, I would get a new extruder and see if that fixes the issue.

I recently moved to an all metal hotend on my S1 plus and had an issue with clogging. Turned out that there was a little gap between the heartbreak and the nozzle which was causing clogging. After a good tightening, it worked well.

Make sure there is no gap between your Bowden/break/nozzle. Check if any filament is seeping between them.

Any recent software changes?

We should enjoy it while we can, it seems that even that is coming to an end.

https://www.gov.za/news/media-statements/water-and-sanitation-releases-2023-full-blue-drop-report-05-dec-2023