Thank you Piercet and TJ for the detailed responses.
I went ahead and bought an Infrared temperature gun (rated for up to 320C) and the hot end is indicating that it is anywhere from 200-210 degrees C on the gun when the temperature is set to 230 C on the Taz 4.1. When the machine is cool the hot end matches the ambient temperature.
While i understand that shiny objects may not indicate an accurate temperature from an infrared non contact source, shouldn’t the variation be less than the order of 20-30 degrees C? Is it safe to assume that the temperature of my hot end is incorrect and the parts require replacement?
As far as the other potential problems:
With regards to nozzle height I usually try to ensure the nozzle is far enough away from the bed to prevent the filament from not sticking. This usually results in a few passes of a bad skirt and re-attempts before the print is commenced. The bed is usually checked for level 1-2 times a day and certainly any time a part remains stuck to the bed that requires a little prying.
Initially I have seen some parts lifting from the bed until I switched to Kapton Tape. With Kapton tape and 3-6mm of brim parts no longer depart from the bed surface. While increasingly difficult to remove the trade off was always considered a success in comparison to restarting due to a failed print.
When the filament started to jam I first checked the idler tension. Adjusting it from 10 cm as recommended to tighter and looser by about 5mm in 1mm increments with no success.
The filament appears to be a high quality and is measured periodically throughout the spool for dimensional accuracy. I’ve used both calipers and fixed measuring blocks to verify its diameter to within 2 decimal places. When i was feeling particularly nerdy I even went as far as to measure it with my cnc machine to verify the measurements of the the measuring tools…
As far as an actual jam in the hot end I would assume that this could be what causes some machines filament to curl when hand pressed through the nozzle. Mine comes out in a straight line with no curling when hand pressed. Outside of that i’ve little idea how to verify a potential jam without the worlds smallest borescope or an additional nozzle (which i’ll probably get anyway at some point in time…