Spoilers of course.
At the end of every playthrough of Oxenfree, no matter what choices are made and who lives or dies, it seems that Alex is trapped in a timeloop forever. However, if you get every Adler letter and find every anomaly, you can send a radio message to Alex in the past and tell her not to come to Edwards Island at all, and instead she, Ren, and Jonas go get pizza. However, it seems that you can still do another loop of the game after this. Did it not work? Is Alex doomed to be trapped with the crew of the Kanaloa no matter what?
No, at least if this theory is true. You see, rather that each playthrough of the game being an example of the same Alex going through the events of the game, every time we pick "Continue timeline" we are instead playing as another Alex in the infinite multiverse. It's not so much that one Alex is trapped forever, it's more that every Alex (except the one that was warned somehow) is fated to go to Edwards Island.
The crew only says it's a timeloop because from their perspective, outside of the normal laws of time and our own dimension, it is. They will be doing this with every Alex forever and ever, so it's really more like they're caught in a timeloop than she is. And the reason why Alex gets deja vu in repeat playthroughs is because the border between timelimes becomes more sketchy (as seen with the scenes where Ren apparently dies and Nona is left alone when Alex and Jonas go to the bridge stand to open the door to the fallout shelter) when Alex first opens the rift and starts communicating with the crew. She's really recalling/experiencing what other versions of herself are doing, will do, and have done.
I'm sure this has some holes in it and I'm sure this isn't completely original, but I more did this to start a WMG page for this game when it was long overdue.