I do have to agree that you should be treating them the same way you would treat a small bank. Think of it this way, if you went down to your local bank to withdraw your money and they didn't immediately give it to you would you ever use that bank again?
Even with the largest banks you can't really just walk in and get HUGE sums on the fly.
I tried to withdraw $25,000 from US Bank at once on the fly to go buy something and they straight up told me no... needless to say shit got a little ugly, a manager came out and they gave me five $5,000 cashiers checks. I had to go to 5 different branches.
They told me in the future for stuff over $5,000 it was best to give them a three day heads up...

My coinbase account was frozen too.
They said it was because I had multiple accounts and instructed me on how to close the others. I did this and now they won't respond back after about 3-5 emails.
I haven't tried to sell there since, but I kind of figure that it is a no go on that as well.
(they don't have any of my Bitcoins of course)
Do you use same multiple accounts on yourself? or have member of the same household having different account?
Multiple accounts tied to one LLC most likely, but I can't recall 100%.