Wow, I could've sworn that I'd set my default to subscribe for reply-alerts to any thread I'd posted, but apparently not. I'm just now (2021 Sep 16 Thu) seeing that you'd replied, seemingly right away, suggesting I provide a savefile.
Luckily, I'm somewhat anal retentive in archiving my saves. (Don't compliment me, it's not a virtue.) Anyways, I posted both saves (my "real" map and my creative map) to https://www.dropbox.com/sh/hnwl36z9d91cggm/AABHyzVd43QqYawcjtDK0i_Qa?dl=0.
I won't be able to dig for archived previous-versions for any mods until at least tomorrow due to real life hecticness, but I did manage to just now test-load both of the saves (I think without overwriting them, but even if I did that, I still have the originals on my hdd) and the in-game alert does indicate that more than one or two other mods have updated since then -- including Rampant, CreativeMod, Fill4Me, and LTN according to the notification.
When I posted this thread, Rampant was on v1.0.8, and I see that it's currently v1.1.1. I just read the changelog, and since v1.0.8, it doesn't immediately seem to me (I'm not a programmer or gamedev by any means) that any of those changes seem relevant to the issue I was attempting to report here.
I will confess that I'd abandoned that main save a few months ago, but I have a current map (an evolution of my overall design goals) with more than 442 A LOT OF gameplay hours -- ACTUAL gameplay hours, I don't ever leave it running overnight, if I step away from my gaming pc it's because I've either paused the game to take a whiz or else I've saved and closed the game client. I do know that I opted to entirely disable Rampant from my current save, because I could always reactivate it at a later time -- and most of my current gameplay goals are somewhat irrelevant to biter-defense anyway. That said, I'd be perfecly happy to tinker with Rampant on my current map (v1.0.8 or the current v1.1.1, or even both) if you can let me know what kind of data and info to keep track of that would benefit your troubleshooting efforts.