Message when issuing a challenge

[TomBombadil711]

When I choose the Gustav Line or Italy scenario for a MP challenge, the following message shows up:

The game has detected that the following files are modified and may not be suitable for multiplayer: equipment.pzeqp
Your challenge will be flagged as custom. Continue?

What does this mean and how to avoid this?

Thanks in advance.

[Kerensky]

viewtopic.php?t=25350

Updates to the equipment file hasn't yet been synced to the version the server is checking for, which is why you are seeing this warning.
There were several balance changes made, but rather than constantly update what the server checks for every time there's another update, better to wait until balancing is complete (there's still much to balance), then sync the server to that version