I've bought only one house this way. I've never sweat so much in my life. It's a very unsettling feeling to drop a certified check off to the lawyer's office for $10,000 the day before an auction. Sure, you have the deed already, and sure, you've gotten the all-clear from your title company, but it's nerve-wracking.
And you can bet that my stomach was one huge knot when I went to the house a couple days later and saw that the locks had been changed by an asset manager!
This was an error; the house was just on the schedule to be serviced. But it still made me VERY nervous.
I don't think you will be able to cure the default by just paying the lender what's owed. At that point, the attorney has the file, and they have the reinstatement amount. The lender doesn't want to be bothered.
In this market, I would be shocked to see a lender call a performing loan simply as a result of the due on sale clause being triggered. However, it's always possible. That's why my suggestion is that you do subject-to deals only when you're planning on flipping the house quickly or refinancing it.