You/your computer has 4 days to complete a FAHB task. If you don't, a copy goes to another computer. If that computer returns the result before your computer does, AND, if the final result has been removed already [canonical moved to master database, removed from result status page, no longer live], your computer's result will be declared "no longer usable", or more direct "Too Late ^ 2".

You don't need studying your logs... visit the Result Status page and see if those tasks are still listed... outside chance, the tasks are listed as "detached", meaning somehow something happened on your client for the server to think that the results needed re-assigning to a different computer.