updating to Renai 2.1 or greater causes conflict with the miniloader (redux) mod:

2025/06/09 19:20:31 Factorio Server: 18.822 Error Util.cpp:81: entity prototype "hps__ml-miniloader-l" (loader-1x1) collision_mask(Modifications: Miniloader (Redux)) must collide with entity prototype "RTBeltRamp" (transport-belt) collision_mask(Modifications: Renai Transportation).
2025/06/09 19:20:31 [18.822 Error Util.cpp:81: entity prototype "hps__ml-miniloader-l" (loader-1x1) collision_mask(Modifications: Miniloader (Redux)) must collide with entity prototype "RTBeltRamp" (transport-belt) collision_mask(Modifications: Renai Transportation).]
2025/06/09 19:20:31 Factorio process exited with error: exit status 1

original server crash was due to something else (detailed further below), and the upgrade to >=2.1 caused the problems.

original issue:

2025/06/09 19:11:23 Factorio Server: 247077.620 Error MainLoop.cpp:1510: Exception at tick 108252595: The mod Renai Transportation (2.0.16) caused a non-recoverable error.
2025/06/09 19:11:23 [247077.620 Error MainLoop.cpp:1510: Exception at tick 108252595: The mod Renai Transportation (2.0.16) caused a non-recoverable error.]
2025/06/09 19:11:23 Factorio Server: Please report this error to the mod author.
2025/06/09 19:11:23 Factorio Server:
2025/06/09 19:11:23 Factorio Server: Error while running event RenaiTransportation::DebugAdvanceActionProcess (ID 277)
2025/06/09 19:11:23 Factorio Server: LuaEntity belongs to surface platform-7 (index 14) but a LuaEntity belonging to surface nauvis (index 1) was expected.
2025/06/09 19:11:23 Factorio Server: stack traceback:
2025/06/09 19:11:23 Factorio Server: [C]: in function 'draw_animation'
2025/06/09 19:11:23 Factorio Server: RenaiTransportation/control.lua:620: in function <RenaiTransportation/control.lua:598>
2025/06/09 19:11:23 Factorio Server: 247077.621 Error ServerMultiplayerManager.cpp:84: MultiplayerManager failed: "The mod Renai Transportation (2.0.16) caused a non-recoverable error.
2025/06/09 19:11:23 [247077.621 Error ServerMultiplayerManager.cpp:84: MultiplayerManager failed: "The mod Renai Transportation (2.0.16) caused a non-recoverable error.]
2025/06/09 19:11:23 Factorio Server: Please report this error to the mod author.
2025/06/09 19:11:23 Factorio Server:
2025/06/09 19:11:23 Factorio Server: Error while running event RenaiTransportation::DebugAdvanceActionProcess (ID 277)
2025/06/09 19:11:23 Factorio Server: LuaEntity belongs to surface platform-7 (index 14) but a LuaEntity belonging to surface nauvis (index 1) was expected.
2025/06/09 19:11:23 Factorio Server: stack traceback:
2025/06/09 19:11:23 Factorio Server: [C]: in function 'draw_animation'
2025/06/09 19:11:23 Factorio Server: RenaiTransportation/control.lua:620: in function <RenaiTransportation/control.lua:598>"
2025/06/09 19:11:23 Factorio Server: 247077.621 Info ServerMultiplayerManager.cpp:808: updateTick(108252595) changing state from(InGame) to(Failed)
2025/06/09 19:11:23 Factorio Server: 247077.621 Quitting: multiplayer error.
2025/06/09 19:11:23 Factorio Server: 247077.624 Info GlobalContext.cpp:769: Deleting active scenario.

That's a weird one but easy enough to fix. Not sure what can be done about the pre 2.1 version but hopefully whatever was causing that was fixed since then?

Your update fixed this, thank you SO much for the quick response, I've been dying to try out all the new goodies of 2.1+ :D