Yes.
This is why people talk about Steem Dollars posing a 'systemic risk'. In a bad enough downturn, the existence of Steem dollars could result in hyperinflation of Steem. It is a very unlikely scenario but possible, and some want rid of SBD simply to close that possibility.
Edit: I only saw your comment once. It's just a guess but Steemit.com nodes might be failing to propagate transactions to the network under heavy load. If that's the case, Steemit Inc simply need to spin up more instances, and maybe handle the error better.
Correct, although I am not sure that the inflation is actually tuned to account for the STEEM value on exchanges. So if I understand right: the STEEM you get from changing SBD is created by inflation, say that STEEM value goes really down and there are large hodlers of SBD, I don't see why there should be enough inflation to produce enough STEEM for them. So if you hodl SBD, STEEM price goes down, you are setting up the system for default, please let me know if I understood correctly. SBD are not a bad idea per se, but they should be emitted keeping in account how many of them are circulating (like government bonds)
The only way default could happen is a hard fork supported by consensus. Building default into the smart contract doesn't really make sense, a default is a violation of a contract (usually with mitigating circumstances).