Only in multiplayer everyone gots 100th lvl after 2nd. No matter what you have researched.

Please check your mod settings values. Dafaults are: first XP level 600, multiplier 1.61 and reductor 0.023,

Default ones. Fine untill dedicated server with friends. Tested solo to make sure on it.

I am playing dedicated server with rpg. No problem here. Single or multi. Can you please list the other mods you are using ?

More than 40. Most noticiable Factorio extended, MSP, Space extention and alot of small mods like balanced splitters, alot of combinators etc. Also rampant and resistant biters + big monsters. Full AAI cars automation also. No more big mods.

May be its caused by reloading game. I generate game solo, save without even movement, then load this in server.

I always do the same thing in my server. Can you share this save ? I have to test with your mods.

Then, may be full modpack? I can drop links in discord, cuz modified few mods from portal, that marked to use as is, no modifications allowed. SuicideParty#0652