Cannot change Global Texture Parameters in a Material Instance (and other similar things)

For some reason, this issue has just started in the last couple of days and seems to affect random projects. Let’s say I have a Material with Global Texture Parameters for Base Colour, Normal, etc. A Material Instance derived from that should allow alterations of these, yes? But not any more… for some reason, no selections ‘stick’. The editor just ignores any attempt to change things.

The image below shows what I mean. The material here is an instance of ‘GM-C-N-ORM’ and has params for Colour, Normal and ORM. The drop-down list (where it currently ‘shows T-PF-Head’) has what I’d expect in it (other textures), but selecting them never actually changes the value. It’s always ‘stuck’ on ‘T-PF-Head’.


In a similar fashion, I cannot change the mesh of a static mesh by selecting it from the list, a skeletal mesh from the list, etc. Essentially, I am unable to use any of the dropdown lists to change an asset reference.

Anybody have any clue why? It’s driving me insane.