Hey Götz,
Yep you’re spot on. Turns out it is purely just a display issue; exported the mesh and textures of the large reconstruction region and visualised in Unity. Texture quality was great, on par with the display quality of the smaller area in RC. Any ideas on what might cause this? Something to do with our configured settings/hardware (see below)? Or just a bug?
CPU: Intel Core i9-7980XE
Memory: Corsair Vengeance 128GB-DDR4 @ 2666MHz
GPU: Asus Turbo GTX-1080ti 11GB GDDR5X (x2)
Mobo: Asus ROG Strix x299-XE Gaming
Many thanks for the advice, saved us a lot of time and guess work!