When running a Tax Claim using the R68 process, records in a selection are not included in the process run because they are locked by a different R68 process. This is shown by the notification on the revenue record:
This transaction has one or more applications on a pending R68 process and cannot be edited.
However, there is no way to determine which process these are locked in other than to go through each instance and check the history for a failed run.
We are currently evaluating this issue and will update this article when we have more information.