Since preparing the Hive nodes for latest hardfork, I noticed that some contracts, including Neoxian Silver, on Hive Engine are calculating staked balance incorrectly. Essentially it is possible to unstake about 10 times in quick succession as the staked balance is not subtracted by correct amount. In the end it leaves about 1/10th of the original staked balance. Obviously I didn't try to withdraw those tokens.
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From @mtl1979