The issues with the cards has our attention and you can rest assured that we are working hard to resolve those. The issues are basically 3 categories:
[Bugs]
As we grow we find more and more corner cases of weird terminals sending us outdated or incorrect data or weird combination of data. This sometimes reveals bugs. We spot them and squash them asap. One of the recent examples: we were receiving online payments with them stating the card was of a "VISA"-type. Ofcourse we only have Mastercard, so our backend declines those. But after seeing the data we started allowing it; despite getting wrong data it was better than denying the transaction.
The Mastercard/Visa network is very old and we get a LOT of weird stuff. Another example is terminals sending us the country of "West Germany". Our backend used to deny those too as it's not an existing country (anymore) and thus a possible indication for fraud. But now we allow them.
What I'm trying to say is we're seeing weird things, and we jump in and try to fix it ASAP. @Eric I believe the Swiss gas station issue was resolved with the deploy of last tuesday night.
[Online merchants]
Send us the weirdest stuff. Sometimes they imitate being a magstripe transaction instead of an online transaction (!). Sometimes they simply don't accept our bin-range, similar to iDEAL we have to contact them to get it resolved. This is an issue with 3D Secure for instance where there are 4 (big) PSP's that don't play along well, despite us trying to resolve this issue for months. You can rest assured that this has our utmost attention. At the same time I believe we have been too careful with online transactions, making whitelisting/etc too cumbersome for the average user. This is something we're looking into now...
[General weirdness with cards]
I think it's also fair to say that Cards sometimes simply don't work. I've had this with many of my cards from different banks. Sometimes something is just off and the thing refuses. I've even had that one of my credit cards didn't work, whereas my bunq card did.
I think it's really sad for you to love us, but leave us in frustration because of these issues. All I can say is that you can be sure that we are resolving / working on the issues that are actually in our control. And I hope there's some solace into at least knowing that we do listen, and we do improve, because we care about our users. We just need some time to properly fix things, one by one.