The 20-year-old music student could hear motorists beeping their horns and shouting so went out to investigate, before hearing the driver calling out for help from within the van.
Cat managed to release the driver but had to come out for a second time when the courier got himself locked inside again – after moving the car just 5ft down the road.
She began filming the second rescue as the driver slid his key fob through a gap in the back door of the van so she could let him out.
The driver can be heard saying: “Can you see it? You need to put that on the door and it should release me, got it?
After Cat opens the door, he says: “That’s twice now, I don’t understand how it’s doing it.”
Cat suggested: “I would say, just don’t get in the back of the van.”
To which he responds: “I’ve got to, I ain’t got no choice, honest to god.”
Cat posted the video on TikTok yesterday, writing: “How did this even happen?”
The video has now gained over 700,000 views with more than 72,000 likes.
Hundreds of viewers left comments on the clip after being left in stitches by the mishap.
@0012s3 said: “I would be too embarrassed to ask for help and have to live in there.”
@TheFamileigh said: “The fact that it’s happened more than once.”
@Jayde said: “I’m not surprised with the weather in Wales at the moment, it nearly took my car door off.”
@BuffRulz said: “No wonder my damn parcels are always late.”
And TikTok user @chrisrowley100 said: “I work for DPD and this happened to me last week. I was stuck in the back for an hour.”
Speaking today, Cat said: “So we could hear lots of cars beeping and shouting and went out to the street.
“He was stuck in the van and blocking up the street so we sorted it and went back into the house.
“Then we could hear him banging and shouting again literally two minutes later and 5ft down the road he’s stuck in his van again.
“He had to give us a fob under the bottom of the door to get him out.”
The driver’s wife commented on the clip yesterday, writing: “To all the Karen’s out there I’d just like to say my husband did thank the guy who let him out.
“The video only captured the best parts.
“He wasn’t happy when it happened but he’s finally over it and we’re all sat here in barrels of laughs watching the video over and over again.”