A day later they wrote back to me that due to the blocking their "representative will get back as soon as possible." It's been a week now and no further response. By the way, I logged in to Spectrocoin on my phone and successfully transferred the remaining money to another wallet.
It's unusual that they asked you for more information about your coins but at the same time you were able to access your account and withdraw the money. Usually when centralized services do a thing like that, you will be blocked until you comply and give them satisfactory answers.
So I conclude, as many of you here have surmised, that the main trigger here was the sender and his reputation - shady Yobit. And at the same time, this is a tip for those who still use Spectrocoin and Yobit and are not aware of the reputation of the latter - these two companies can not be intertwined in any way. Avoid making transfers from Yobit to Spectrocoin, as you may have problems, bigger or smaller.
It's generally not a good idea to send crypto from one custodial service like a casino or exchange to another custodial service. It's safer for you to withdraw your coins first to a non-custodial wallet, whose keys you and only you control. After that, you transfer them wherever you want. If there is a problem with the initial transaction (custodial service to custodial service) and the recipient has to send the coins back, they might get 'lost' because the intended recipient didn't respect all the deposit instructions that the other platform requires or the addresses changed. You will then have to contact support asking them what went wrong. It's better if you control the wallet that sends the coins in the first place.