I have a page in my app with 2 Combo/Dropdown boxes on 2 seperate forms. These have various visibilities/active statuses set depening on how the form is currently being used, controlled by a variable and various other settings. This is probably unimportant.
I have one status box fed by a variable named "availableStatuses", this variable is changed by <things> to update the number of statuses on view. It drops down and allows me to select items from the list :

This Meshes with the current status of the "availableStatus" collection :

All good, all working. I have a second combo box set up almost identically on a second form on the same page that just.... wont behave. Its fed from a collection named "itemStatuses", which currently looks like :

Despite this the box looks like :

It has the correct default, but does not have a dropdown arrow to allow me to modify the value. The form is set to View but I've manually set this control to Edit. Amazingly if I set the control to Disabled it shows :

Any idea whats going on here?