RT 5.4 and very slow file browser

RT 5.4 appimage on Manjaro

Sometimes, RT is extremely slow when using the file browser. This afternoon, I have a directory:

  • 3332 items
  • 1638 images
  • the rest are Digikam XMPs and PP3s

It took 52 minutes! I had time to a few chapters of AE Van Vogt: The Wizard of Lynn

Only RT and htop running. 8 CPUs, no swap, plenty of ram.

Other times, on similar directories, it much faster a few minutes, less than 5.

My file browser settings are:

What am I doing wrong?