WSI is not being visualized

Background H&E WSI TIFFs are not visualized at all in xOpat, producing just empty views:

Example: https://mlflow.rationai.cloud.trusted.e-infra.cz/#/experiments/5/runs/4a0c581e93ee4ef893db88bc130d510b

Minimal reproducible example using background WSI only.

defaults:
  - default
  - background: drive
  - save: mlflow_standalone_run

title: FLASHxNanozoomer - Nanozoomer Report
background:
  dir_name: /mnt/data/IIPImage/matejg/FLASHxNanozoomer/Nanozoomer/wsi_c
  layer_name: Nanozoomer WSI
save:
  metadata:
    experiment_name: Testing
    run_name: FLASHxNanozoomer - Nanozoomer Report
    description: Comparison of two scanners using Mann-Whitney U-Test and Kolmogorov Smirnov test on predictions.`