There is an assertion in the removeNotFoundBatchLoadableEntityKeys method of the BatchFetchQueueHelper class that seems to be wrong[1]. This error can make test cases fail unexpectedly.
When reaching this method having the results list with a size lower than the ids array (Because the ids array has duplicated values: this can happen when using the padding fetch style), then the assertion can fail.
I think that the ids.length is not the size to check in the assertion. Attached patch with the proposed solution.