Help with textures issue


I’ve not used blender in a long time and I’m a bit stuck. Probably doing something stupid so thought I’d asked for help.

I’ve been using qubicle to make some models to be imported into a game engine. I exported as FBX and imported into blender without issue. I removed some unwanted vertices and now the texture appears strange and has what looks like a gradient.

As you can see the altered model (right) has light area not present on the unaltered model (left). The UV and texture appears unchanged so not sure what is causing this.

Any help would be much appreciated.