I decided to try out a purge after months of ignoring it.
Luckily, it will not spawn in the open sand next to my purge base.
I have had purges in this area, previously. Anyone else have an issue with this area?
If you don’t get any other responses, I’ll try to find some time to test at some point. I’ve got a save with a purge base in the right area (nestled back towards those rocks you’re looking at in the screenshot), but I know steam wants to do a bunch of updates right now and I don’t have time to sit through all of that. Hopefully some others can test sooner, but I’ll get to it when I have a chance.
I managed to get a bit of time. Purge started successfully - this is in singleplayer, so what Xevyr said in his video about heavy load on the server could still be in play, because that wouldn’t apply for me. It shouldn’t matter about numbers of pieces involved (because my purge base is unnecessarily heavily decorated) - but the route to the treasure room is very straightforward - straight in an open entrance, up several flights of stairs and only one door (in case pathing complexity could be a factor).
One thing I did notice was that the enemy base set up a lot further away than purges I had done previously in that area. Obviously this could just be coincidental, but it could also be a change that applied since the last time I did a purge here (which was quite some time ago).
The purge base has its entrance roughly where the dried trees are in your screenshot, maybe a little further back towards the gap between the rocks. Previously I’ve had the enemy camps spawn either on that first set of dunes to the left, or up on the raised area to the right. This time the camp was pretty much all the way back to the entrance to the UC, so noticably further away. As I say, I can’t be sure that is a result of a change in radius required, but it could be. At least it proves it’s possible to get a purge to spawn in that area (though it might require all the variables to be right).
Sorry I couldn’t be more help. I hope you’re able to get it sorted out.
@DanQuixote and @Tephra , thanks for the replies.
I removed and rebuilt my purge base about a hundred yard east. It’s a spiral design without doors and I decreased the size of the spiral by about a third.
I am not certain what changed enough, but purges are now being triggered successfully.
Again, thanks for the input and information.
In this particular place something ain’t correct that’s true . Like you sometimes i had to destroy and rebuild also in order to accept a purge. Maybe it needs investigation or maybe we were both unlucky in the end .
Well, whatever did it, I’m glad you got it working 
You’ve definitely moved closer to where mine is (though the back of mine is closer to where that little pyramid is). As you can see from the screenshot, I went with a straight run from the open archway (beneath the dragon head) up to the one door on the treasure room at the top of the stairs (and I wasn’t kidding about the unnecessary decoration 
(and yes, that is a completely pointless garden out the back as well, because I could…)
That might be full of “unnecessary decoration” but it’s absolutely beautiful! 
Fact.
I am not visually artistic enough to do such a thing, but I can sure appreciate it.