Today server crashed, I dont have a lot of information. Here's the log:

56807.288 Error MainLoop.cpp:1288: Exception at tick 14921744: The mod RPG System (1.3.3) caused a non-recoverable error.
Please report this error to the mod author.
Error while running event RPGsystem::on_gui_click (ID 1)
RPGsystem/control.lua:40: attempt to compare nil with number
stack traceback:
RPGsystem/control.lua:40: in function 'RPG_format_number'
RPGsystem/control.lua:591: in function 'update_char_panel'
RPGsystem/control.lua:868: in function 'expand_char_gui'
RPGsystem/control.lua:826: in function 'open_close_char_gui'
RPGsystem/control.lua:1168: in function <RPGsystem/control.lua:1161>
56807.288 Error ServerMultiplayerManager.cpp:92: MultiplayerManager failed: "The mod RPG System (1.3.3) caused a non-recoverable error.
Please report this error to the mod author.
Error while running event RPGsystem::on_gui_click (ID 1)
RPGsystem/control.lua:40: attempt to compare nil with number
stack traceback:
RPGsystem/control.lua:40: in function 'RPG_format_number'
RPGsystem/control.lua:591: in function 'update_char_panel'
RPGsystem/control.lua:868: in function 'expand_char_gui'
RPGsystem/control.lua:826: in function 'open_close_char_gui'
RPGsystem/control.lua:1168: in function <RPGsystem/control.lua:1161>"

2177.095 Error MainLoop.cpp:1288: Exception at tick 15033227: The mod RPG System (1.3.3) caused a non-recoverable error.
Please report this error to the mod author.
Error while running event RPGsystem::on_pre_player_died (ID 42)
RPGsystem/control.lua:1234: attempt to perform arithmetic on local 'NextLevel' (a nil value)
stack traceback:
RPGsystem/control.lua:1234: in function <RPGsystem/control.lua:1225>
2177.095 Error ServerMultiplayerManager.cpp:92: MultiplayerManager failed: "The mod RPG System (1.3.3) caused a non-recoverable error.
Please report this error to the mod author.
Error while running event RPGsystem::on_pre_player_died (ID 42)
RPGsystem/control.lua:1234: attempt to perform arithmetic on local 'NextLevel' (a nil value)
stack traceback:
RPGsystem/control.lua:1234: in function <RPGsystem/control.lua:1225>"

i think it is a conflict with MSI II 0.8

not related to msi. Have you changed rpg mod settings like max levels or something?

Yes, Level set to max (200) and max settings per Level to max as well (30).

I guess I found the problem. Check Discord pm if possible. I think its faster to verify for both sides.