I received the following error code while on a play through
The mod Rampant (3.3.2) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event Rampant::on_tick (ID 0)
Rampant/libs/BaseUtils.lua:238: attempt to index field '?' (a nil value)
stack traceback:
Rampant/libs/BaseUtils.lua:238: in function <Rampant/libs/BaseUtils.lua:232>
(...tail calls...)
Rampant/libs/BaseUtils.lua:451: in function 'queueUpgrade'
Rampant/libs/BaseUtils.lua:700: in function 'processBaseMutation'
Rampant/libs/Processor.lua:417: in function 'processNests'
Rampant/control.lua:1011: in function <Rampant/control.lua:969>

Do you have a save that you are willing to share?

I got this same issue, uploaded a save file here: https://forums.factorio.com/viewtopic.php?p=585047#p585047

I believe the issue is because in the middle of a game with both Natural Enemies Evolution and Rampant I turned off all of the Rampant factions. (World: Acidic Biter Faction - Disabled, etc).

I got it to stop crashing by changing BaseUtils.lua:238 to:

    local factionAlignment = UPGRADE_LOOKUP[baseAlignment]
    if not factionAlignment then
        return originalEntity.name
    end
    local factionLookup = UPGRADE_LOOKUP[baseAlignment][t]

but that's with 0 experience in lua and 0 understanding of your mod code so I'm not exactly sure how much I'm breaking with that change

Version of rampant: currently 3.3.2 (or 3.3.3? I have the 2 day old version but it seems to have an invalid version number) but before it crashed I had I think 3.3.0
What is your map evolution: 0.400488
Was Rampant added at the start of a game: yes
What mods are you using? (Listed in the forum post)

this should have been fixed in 3.3.3. What do you mean by invalid version number?

The Factorio mod manager thinks that 3.3.2 is version 3.3.3. See: https://imgur.com/a/9r7liTS

The mod manager thinks that the latest version is 3.3.3 and thinks I have the latest version but it's showing details for 3.3.2 and if you download Rampant it gives you the 3.3.2 zip instead of the 3.3.3 zip available here.

I second the last post, Mod Manager downloads a wrong version of the mod. Can something be done about this or do I need to update the version by hand?