3D map view loading one mega tile

[Adam Steer]

Hi all

I'm experiencing a persistent issue with QGIS 3D map views loading up one mega-tile instead of breaking views up into smaller, more detailed tilesets.

It's for quite a big area (900 sq km), and worked fine a few years ago (see: https://www.spatialised.net/mapping-avalanche-risk-factors/).

Using the same project, I'm now unable to recreate the detailed 3D views I used in the article linked above.

Recreating the project from scratch using the same datasets, I have the same result - one mega-tile in 3D views. What I expect to see is a *lot* of tiles loading as I zoom around.

Where can I look for any messages which might help unpack this issue? 

...and is anyone else experiencing this?

Machine config: ubuntu, 64GB RAM. Issue persists whether openCL is used or not.

QGIS version: 3.34.1

Loading the same project up in QGIS 3.18 - 3.28.8 (mamba install), 3D views behave as expected. I can spend some time in Mamba iterating over versions to find the break (maybe). Have verified that a mamba / conda installed 3.34.1 has the same  (one mega tile) behavior.

Hints welcome!

Thanks,

Adam