About 'spurious stop'

[houlinlin]

There is a sentence described like this ' SsXpb-II showed a
single start site mapping at -4 from the first ATG of the ORF,
and a site internal to the ORF (+10), likely due to a spurious stop of reverse transcriptase. ' in an article named'Transcriptional response to DNA damage in the archaeon Sulfolobus solfataricus' . And I am confused by the phrase'spurious stop'.Would anyone please tell me the accurate functions of the 'spurious stop' mentioned above?