Yesterday I requested withdrawal #7 and #8 of 0.03 and 0.3 BTC (I mistyped on the first withdrawal attempt).
Both withdrawals have been rejected few hours later.
This happened for the first time. They didn't inform me by e-mail.
Today I asked them for the reason. They answered the fee could have been too low though I used the default value as always. The fee has never been an issue before.
So I requested a new withdrawal of 0.6 BTC which is pending for hours once more. I have a feeling it'll be rejected again.
Hope this will not end up as a new case in the "scam accusation" section...
I think the reason for the rejection of your withdrawal is actually quite plausible.
The BTC network is suffering from huge congestion right now and therefore
transaction fees have increased.
E.g. the standard fee you used in the past may not be enough anymore, if the mempool is as big
as it currently is:
https://blockchain.info/unconfirmed-transactions
This special situation might make it necessary that you increase the fee value, if you make another
withdrawal.