"Create" button doesn't work to create linked issues on only one project

[Alex Beech]

When creating a linked ticket from one project to another the 'create' button on the screen does not action.

error of 'An invalid form control with name='61f2277b-2791-4661-9630-955d245528ff' is not focusable.'

I have disabled all my add-ons one by one and this makes no difference,

This also works on all other projects. Just one project has this issue.

[Marion Hederer]

Exactly the same issue here! @Alex Beech could you resolve it? 

[Nic Brough -Adaptavist-]

One of your administrators has added some "clever" code to a field that exists for this project.  You will need to get an admin to remove it, as it's broken.