I have noticed that if I type /wasteland or /wastelands they go to the same place but sometimes some of the portals don't work.
When ever the portals dosnt works just keep typing /waste untill you get to that outpost you wanna go to
Here is what I have experienced ... When I type /waste I am teleported to one of the 9 Wasteland spawns. It is random which of the 9 locations you TP to, and this is by design, so that the center portal is not the only one explored/mined. I have noticed that when I arrive at a spawn other than center spawn, that not all water/quartz TP's work. My fix is easy, I type /waste, then I go to the center TP, and then all 8 other TP's seem to work just fine. Hope this helps.
There is some weird problem with the code for that but I can't figure it out, reloading the chunks should help, so go into a different portal.
When I go to the Wastelands, I usually have either chosen already what direction I want to go in from Live map or I am returning to a location I've already been. To avoid going to a random outpost and having to go back, I have been going to /town first then through the portal there which takes me to center spawn. The portals all work when I do this and I can decide where to go from there.
I admit that I find it confusing. It may be because all the outposts look the same. The other night I went to a random spot and set up to kill some Withers then went back to Town for something I forgot. When I returned I had to go through all of the portals trying to figure out where I had just been. It was worse that I was rushing too because my Reis map wasn't updating immediately and they were all looking the same or different than I expected on Reis until I figured out that I had to wait for it to catch up. I just need to train myself to treat it like a parking garage when I use it and remember where I parked before I go through.
When i got to the wastelands Portal area, and go in the portals it teles me back 3 blocks away from the portal.
I think you're probably being teleported to a different outpost - just you don't realise it, since they all look the same. A message will appear in chat when you enter a different outpost. Either that, or you're going through the portal for the outpost you're currently in.