“Warning, database corruption detected. Switching current form to default”

Perhaps someone is making one-species Omnitrix knock-offs that force themselves onto someone nearby and transform them into the encoded alien?
The one-species restriction would allow the transformation to be sustainable for days to weeks before timing out - plenty of time to cause chaos from the victim's confusion, then when they're finally getting used to their new form, the device times out leaving them back in their boring old body.
Then it's up to the once-again confused victim to decide: whether to embrace their new Alien form and attach the device onto themselves again for another period; or choose to dispose of the device somehow and put the ordeal behind them, with the taste of alien power tempting them to retrieve it again; some might even consider placing the device where someone they know will come across it...