Withdrawing funds from exchanges can fail

[sputniky]

There are several reports that withdrawals from exchanges like e.g. Citex do sometimes fail. Exchanges say that they sent the coins and provide a TX for that, but this TX doesn't exist on the blockchain, so it seems that it was not accepted by the nodes.

One example is with user Rand5667 from Discord server, where it was lost in June 2021:
https://discord.com/channels/460867662977695765/624072580571332618/851085620252246016

After about 3 days it was recovered properly by Citex, and withdrawn properly a second time.
Neverthreless this is an odd situation which should not happen. It is very frightening as big amounts can be invloved. Also it locks MCM for several days which is annoying, with big fears in the mean time. Finally, it might also complicate things for the exchange if they have to implement a certain check like identifying the pseudo-blocks, which is an overhead for them.

An investigation should be done on this so that we know what happens really on their side, and if verified that it is on the nodes, a fix should probably be provided.
If there are several reasons for failures, all should be reported and another ticket opened by type of bug.
People can also report their communication with the exchange about it here so that it provides more info that we can track.
Currently, we don't know how to reproduce this bug.