Windows 10 keeps changing my default programs

I didn't even call him a name - I said he was obtuse....and he is. 

First of all - he is NOT a Microsoft employee - there is no "Microsoft" by his name on his replies as you see when a real Microsoft employee responds.

Secondly - his logic that "if it is not occurring on his computer, then the problem does not exist" is EXACTLY why people hate computer support techs. It reminds me of when working desktop support at my previous job, my co-worker got a call from a user who was complaining that the network was "down." My co-worker said - I'm connected, so it can't be down. A simple 10 foot trek to the computer room would have told him that one of the switches was down. Our floor was okay, but the floor above was down. 

Point being, Sir Charles, if you are still reading the responses.....don't be so quick to say that it is not a problem, and that even if it were a problem - that it's not the fault of Microsoft. Microsoft has made PLENTY of mistakes in the past; and a simple error in the code would not surprise anyone (except you, of course.)

I opened this thread last summer at the height of my frustration with this issue - and found that I am not the only one with it - even though some "experts" say it's not an issue. Since that time, I found a solution that has resolved it for me. Tom (Hyperlogic), Stargateok, and others - I hope someone from Microsoft responds to this thread with some REAL troubleshooting for you. Good luck.