This was a bug spawning into a ravine map, my colony was set to start on the ground instead of pods. one of my characters were visable in the main visable area, and my second character was in an unexplored area so I could not see them and could not get them to the other character, they spawned on the other side of the map in a small opening near edge of map.
The problem seemed to be that each character spawned at a seperate opening in the edges of the map instead of together, and the "explored" area was only for one.

In tunnelworld maps when there is a pod drop you can't jump to location but items still get on the map. either disable drop pods fro them maps or make "show location" possible (Items now don't drop in one are but randomly across the map). Also, in the tunnelworkd oasis you could make a small hole above the lakes so that colonists can see light and maybe be able to grow a few things near them lakes. The middle of the lakes could also be deep water instead of shallow thus making fishing possible.

Thank you for making this awesome mod, and please continue working on it. Have a 5star

every time I get a rescue mission on an island. the refuuge is dead and drowned.

unable to use this mod with MAllorn forest from LOTR elves mod, creates this error:

Could not regenerate layer Verse.SectionLayer_Watergen: System.NullReferenceException: Object reference not set to an instance of an object
at Verse.SectionLayer_Watergen.GetMaterialFor (Verse.TerrainDef terrain) [0x00000] in <filename unknown>:0
at Verse.SectionLayer_Terrain.Regenerate () [0x00000] in <filename unknown>:0
at Verse.Section.RegenerateAllLayers () [0x00000] in <filename unknown>:0
Verse.Log:Error(String, Boolean)
Verse.Section:RegenerateAllLayers()

took me awhile to narrow down this error but once i removed this mod it started working again

I don't know what the lotr mod changes on the mapgen. I thought it just adds a normal biome but doesn't seem so. If another mod also drastically changes the mapgen, chances are high it's incompatible.

There are a few bugs on islands and caves, since these biomes are so different from normal gameplay. It's hard to track them down and/or to fix them.

I'm not sure if it would break the feel of the cave maps, but some caves in the real world do have small openings to the surface where light can shine down, even if extreamly rare, if you had very small openings where ship chunks, pods, ect could actually make it to the surface would that work in fixing the issues that they have no place to "spawn"?

Yes it would. It was a design decision from me to make no openings, although at that point I didn't know Rimworld has so much trouble with it. I like to think these caves are deep under the surface so even if there is an opening, it's probably so long and not straight up that sky isn't visible. But I may change this if I can't fix the problems coming with this design.

Having issues with Tallgrass Prairie terrain type, which I assume is from this mod given that I have no other biome mods going. Can't start a new colony on this terrain type. So far all other terrains work. I have quite a few mods going, and will likely start doing some narrowing down this afternoon.

Error log here:

http://www.filedropper.com/rimworldbiomeerror

There is no biome calles Prairie, but I assume you mean Savanna.
These errors seem to happen in some special situations with the map generation. I could not find the source until know to fix it, but I'm working on it.

For now you can try a different seed or location. The errors only happen on some maps, so a different savanna tile may work correctly.

Turns out it was Nature Is Sweet creating that biome. My mistake.

Hey, I settled on an archipelago and i've noticed a few odd behaviors:
1. The wildlife eats all the natural plants and starts starving pretty quick, this leads to them swarming your gardens within roughly 5-7 days (I was on naked brutality so there wasnt much hunting going on). Not really sure what could be done about this, either more plants need to grow or there needs to be fewer animals, or maybe more predators.
2. The ruins and steel patches inside the mountain have soil under them. As far as I remember this isnt vanilla behavior. screenshot included: https://i.imgur.com/LsbB3Ao.jpg

1. The new vanilla plant generation acts a bit weird on the custom terrains from this mod. I need to patch or rewrite it. This problem was known but thanks for the numbers, such details are always helpful to get the balancing right.
2. Also known but didn't have time to look at that. I'm currently working on that part to integrate new features, that will probably solve this problem and readd stone unter island mountains.

For some reason my cave worlds will spawn without ceilings, solar panels usable, mushrooms dying off pretty quick, etc ... can this be a conflict with "Advanced Biomes" or do you have any idea what could cause this?

This one is 3rd place in prop after Core and Hugs Lib.

A conflict sounds reasonable but hard to say. An output log would be helpful to see if any error occur. Can you load your cave world als upload and link a HugsLib log (ctrl + f12 hotkey)?

Can confirm that having both advanced biomes and terra project causes cave oasis maps to generate without a ceiling.