The train has been removed from service, park officials said.
A woman captured video of the faulty door over the weekend and posted it to her Instagram page.
The train picked up passengers from the ticketing transportation center, not far from Magic Kingdom, officials said.
The woman who captured the video didn’t want to be identified, but told WFTV that she was concerned because there wasn't an alarm or latch to catch the door. She said the attendant tried several times to get the door to close, but was unsuccessful.
No one was hurt, but the park visitor said before she boarded, it appeared the train was already having an issue with the doors.
The parkgoer said she posted the video to make sure Disney takes steps to prevent this from happening again.
A spokeswoman for Disney said the train is one of 12 serving the Disney World theme parks and properties.
She also said there is a phone in all of the cabins that connect passengers to the train pilot, in case of emergency.
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