I have had a very similar issue. I am on my second charger and it has stopped working. I have tried all of your suggestions, they worked when the charger performance first started to degrade, now these techniques no longer work.
Do you have a solution for this problem? Buying a new Microsoft charger will probably solve the issue short term but I am very concerned the new charger will break over time.
There is an obvious design flaw with the Microsoft charger, is there a 3rd party offering made with better quality?
I am thinking of dropping the Surface due to this issue. I cannot be sure I will be able to use the device from one day to the next because of the chargers intermittent functionality.
Thank you,
Edan