Dell laptop external monitor not working on docking station

I have contacted my IT department for this but they are at a loss. I consider myself pretty comfortable with PCs and have built a few myself etc but I don't know the answer to this one, so thought I'd reach out to the internet nerds and see if anyone has come across this:
My work laptop is a Dell, which I use on a docking station both at home and in the office (I am a hybrid worker)

It works perfectly, except with any external monitor. I have tried it on about 10 different docks all with the same error.
My IT dept have had a thorough look and come up empty. They have tried reimaging the laptop and running Dell diagnostics but all comes up fine.
The Windows monitor settings are correct, and I can plug a monitor into the laptop's HDMI port without issues. That's what IT told me to do as a workaround as they don't have the budget to replace my laptop unless it was properly broken, and yes it's not difficult to do but I don't really fancy doing this until after summer which is when I'm told I can get a replacement.