That tip has had it - Weller WMRP RT3

I've had difficulty soldering properly with well-established settings for quite some time now. I had to set the temperature to 400°C to get just decent operation. I measured the temperature as well and it was fine.

Looking at the tip closely revealed significant erosion, hence lack of physical contact with the PCB and miserable heat transfer.

For the time being I chose to grind the little peaks away, fully knowing that the plating will deteriorate even faster, but at least I can get stuff done for now. I'll need a replacement pretty soon.

After just 3 years of moderate usage, the plating is gone. I have a feeling most of the damage was caused by the brass shavings used to clean the tip.

Now I'll have to fork out 40 something to buy a new one, as the heating element is inseparably fused to the tip.

You cannot just replace the tip itself and keep the fully functional heater / sensor / pencil, you have to throw away perfectly good hardware, just because the tiny tip is EOL.