I have had nothing but good luck with the new concave buttons. They seem to make better contact. Keeping them clean is a must though. (that includes wiping clean the bottom of the battery also.
As far as separate buttons for sale, Epic and Vaporlair had 350 & 500 tubes for sale. That's what the spare buttons are for. Smpl still sells the 350 tubes and spare buttons also.
Nope.
The free replacement buttons are meant to resolve the hot-button flaw in the initial run.
Lots of members here have had the same issue.
VL is doing the right thing by replacing them for free, but a little QC before selling them would have prevented this fiasco and saved them a ton of cash.
Amateur hour as usual in this industry.