I don't think Sinbad is going anywhere, I guess it is routine maintenance and they will come back more strongly.
If there was any other reason, they could have written more clearly and people would trust them. So I will assume that we are here for a little maintenance and it is time to be a bit patience.
Services blender.io and blenderwallet.io are closed for maintenance. Completion dates for technical work will be announced later.
Your funds in Blender Wallet are safe. You can wait for the service to open or access them with a mnemonic and passphrase in the Electrum wallet or any other compatible wallet.
Dear users, the service is closed for update and maintenance, the date of works completion will be posted later.
There is a similarity between the two messages, but beyond all theories, let's see what will happen next Thursday (payment day).
[1]
https://www.wired.com/story/sinbad-crypto-mixer-north-korean-hackers/By the way, what happened to blender ? Were they closed permanently after this message?