What does the error message 'Outdated asset data' mean?

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The error message ("AssetManagementException[am.outdatedAssetTCN]: 
Outdated asset data: 123[428570-v1-c0-tcn2-
ccn2]. Please Retry") ... points out that two processes try to work on the same asset. 
The faster one wins, the second one gets
 this error message.

Every process generates a transaction-control-number (tcn) which increases about one. The slower process evaluates that his tcn is out of age and breaks with the upper error message.