It seems like the most recent update caused some issues.
This happens even with just this mod.
The following is the sentence that was displayed:

Failed to load mods: Armored-train/data.lua:8: module assets.wagons.minigun-platform-mk1.minigun-platform-mk1 not found; no such file Armored-train/assets/wagons/minigun-platform-mk1/minigun-platform-mk1.lua no such file Armored-train/assets/wagons/minigun-platform-mk1/minigun-platform-mk1.lua no such file core/lualib/assets/wagons/minigun-platform-mk1/minigun-platform-mk1.lua
stack traceback:
[C]: in function 'require'
Armored-train/data.lua:8: in main chunk

Mods to be disabled:
• Armored-train (0.5.4)

I used Google Translate, I hope it's translated correctly.

same report.

ya i got the same bug. not sure how but its not registering the asset file. might be a misstype somewhere that was hard to spot.

Folders "Turrets" "Wagons" -> "turrets" "wagons" in Armored-train/assets/

Fixed. Messed up with folder names and archives. Thanks for report