xref weird behavor

Okay so this is happening.
All paths are visible and shared to all computers. All computers have full access.

This projects contains a main max file and have 8 buildings xrefed to it. All paths are network paths.
After I hit render this happens:

  • Sometimes only 1 xref fails to load, so all buildings are rendered fine and 1 has missing buckets.
  • Sometimes all of the xrefs fails to load and buckets look like a chess board.
  • Sometimes xref materials fail to load, so buildings are in-place but materials are chess board.
  • Sometimes is works like nothing happens.

Every time it feels like a lottery.

What am I missing? All machines successfully completed a backburner job.
Also when I open the xref on each machine separately - there are no issues.

Are you using 2018? Apparently they fixed some X-Refs issues, to me it is still not fully workable, so sometimes I opt for the VrayScene option, much more reliable even if it is in development phase.