Screenshot: https://i.imgur.com/YNLAthX.jpg
Not an isolated island or anything. Big continent with lots of landmass interconnections.
1) Attack waves get stuck in large numbers on shores. Looks weird, but not really gamebreaking
2) Attack waves can spawn in the middle of a water body. Looks weirs AND has potential to wreck unprotected infrastructure because why would I protect parts that enemies should have no way to path to.
Most Rampant settings are default, except: enemy variations = 4, shrink nests and worms = on (dont remember changing that from default), enemies fill water on death = off, starting peace duration = 40
Additional mods that may be relevant: Combat Mechanics Overhaul, Rampant Evolution, Alien Biomes, Space Exploration, Jetpack (could be messing up the pathfinding map or something, idk)
Save created in one of the previous versions, somewhere in 3.3.x range, cant say for sure. Factorio experimental 1.1.81 (to fix one of the fatal crashes that happened on stable 1.1.80 with rampant)