Mercatox is shady. No bad experiences with them myself as I have avoided them based on the experiences of others but mercatox has a long history of shady practices that are well documented especially when the price of XRB (now Nano) climbed exponentially in December. People had their coins locked up for months on there. I would not be surprised at all if what you are noticing is very real. I would also advise not using mercatox moving forward.
I don't think this is correct at all.
And I can say that with near certainty, since I was buying up RaiBlocks/Nano at exactly that time. Mercatox was fantastic. Still is. BitGrail was the other exchange that was active with Nano, and that turned out to be a gigantic scam.
https://cointelegraph.com/news/strange-twists-and-turns-of-nano-and-bitgrail-since-the-150-mln-hackI got lucky with BitGrail and was able to withdraw my Nano. But I think you may be mixing up the two exchanges.
Wanted to clear that up so the community can hear another data point, one based on of months of direct, personal experience, as opposed to hearsay.
As always, stay informed and make up your own mind tho. Stay safe out there.