If for some reason distributed rendering does not work as expected, it is advised to check the images generated by each render node. To do so:
1. On master PC: go to Render Setup > System > Distributed Rendering and check "[DEBUG] Retain EXRs" checkbox
2. On master PC: start distributed rendering
3. On master PC: stop it after at least 1 pass (or after the problem appears)
4. On master PC: hover your mouse cursor over "[DEBUG] Retain EXRs" to see path to the folder where the received images will be stored
5. On master PC: go to that location and inspect the EXR files received from each render node