Blocky and incomplete mesh output despite good input

[mrlechuck]

Hi,
I'm getting very blocky and incomplete mesh output from Instant-NGP, even though the input seems solid.

Input video: good quality (1080p, stable, slow motion around object)

Extracted ~80 frames with ffmpeg

Used COLMAP (automatic_reconstructor) to get poses

Converted to transforms.json via colmap2nerf.py

Images load fine in Instant-NGP

Still, the mesh looks low-res and unnatural — like rough cubes.
Could this be due to bad camera intrinsics? Or insufficient pose accuracy from COLMAP?

Any tips appreciated!