Qhapaq Nan and how they work. Do they sometimes disappear?

[Hawaiian]

So I've been trying these out with the Inca. Pretty cool. I built 3 over a few different mountain ranges, and I notice that sometimes they disappear. So I have to build it again. Is that a bug? Or are you only supposed to be able to have 2 locations?

 

[Lord Lakely]

Unique tile improvements vanish when a rival AI gains control of the tile they were built on.

 

[Hawaiian]

Since these are on mountains, does that mean when a rival's borders encompass it? Because that didn't happen. But enemy units were around it sometimes.

 

[Tech Osen]

Improvements can disappear when hit by natural disasters though I'm not sure if this goes for mountain based improvements.

 

[ExemplarVoss]

If you click on the icon, they go away.
Not sure why.

 

[StrideColossus]

Improvements can disappear when hit by natural disasters though I'm not sure if this goes for mountain based improvements.

Can confirm this is the case. I had a storm sweep over and destroy the tunnel (had to go back through auto-saves to work out what happened to it!)
Oddly enough traders don't seem to mind, they carry on through the mountains!

 

[Sostratus]

So I have to build it again. Is that a bug?

Can confirm this is the case. I had a storm sweep over and destroy the tunnel (had to go back through auto-saves to work out what happened to it!)
Oddly enough traders don't seem to mind, they carry on through the mountains!

I had a Qhapac appear to be obliterated by a megacolossal. I built a ski resort on the tile without realizing it was gone. But lo and behold, my units can still move right through.
I'm starting to think that the way they coded mountain tunnels is suspect... Perhaps they were having issues getting the coding to go backwards and remove movement access.
Related to eruptions, did anyone notice if volcanoes added fertility to incan mountains?I had a volcano erupt and claim it gave fertility to a lot of tiles, even though it was surrounded by mountains with only 1 free hill.

 

[iammaxhailme]

Mine disappeared becuase a volcano blew it up, but I don't think I've seen one disappear for any other reason

 

[gunnergoz]

I like a world with a bit of mystery to it. As long as it is not too crazy and breaks suspension of disbelief. (Yes, I do mean that, I have to feel Civ is not entirely fantastical, like with hovering sci-fi mountains, etc IMO, GDR's belong in another game, for instance..