"The system cannot find the file specified. (0x2)" tends to happen when there was a (non-revoverable) "Client Error" (actually App-error) before the final Result file was written. However the "exited with zero status but no 'finished' file" issue should be treated as recoverable in newer Apps and the Client should simply restart this Result.
BM

Workunits failing with error - no finished file
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As you see from the message log, the Result is simply restarted right after the "exited with zero status but no 'finished' file". The Result finishes minutes later, so if there happens a Client Error causing a failed Result it's not related to the "no 'finished' file" problem.
The Client Errors of the second WU you mentioned all happened with App 4.75, and these errors are the main reason why we brought out the newer Apps which should have this probem fixed.
BM
BM