There is an assertion in the removeNotFoundBatchLoadableEntityKeys method of the BatchFetchQueueHelper class that seems to be wrong. 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.