TLDR; earlier today, Dragginz experienced an SNS upgrade issue. We believe the issue was triggered by old proposal data. We are continuing to investigate. We ask you to not upgrade SNSes before we know more.
Earlier today, the Dragginz team reported a few failing SNS upgrade proposals in the past hours (see Dragginz Proposals - ICP Dashboard). The NNS team looked into these failure cases. We identified three distinct failure reasons:
Duplicate upgrade proposals that were submitted within a very short period of time from one another
Upgrade proposals that started executing while other upgrade proposals were executing.
Upgrade proposals that started executing, but never completed due to the WASM version not getting upgraded to the expected version.
The first two failure reasons are expected, i.e. the current SNS upgrade design does not support concurrent upgrade proposals. (The general recommendation is submitting one such upgrade proposal, getting it voted through, and only then submitting the next upgrade proposal.)
The third failure reason, however, is most likely indicative of a bug in the post-upgrade hook of the latest published SNS Governance, which panicked due to some old proposal data in the Dragginz SNS. We are currently reproducing this issue on a local testing environment, and will come up with a solution shortly.
While the risk seems to be low for SNSs (other than Dragginz) to submit upgrade proposals right now, we ask the teams to avoid doing so until the proper solution is ready.