Just like the title says. After several hours, days, of gameplay I am getting this message. No new mods added. No updates made (except one, I'll explain below). No enemies nearby. I'm not being pursued. I am under my carryweight. Happens both on and off my horse and with different companions. Location doesn't matter.
I have two games going, each under a different profile in Mod Organizer. They do not have all the same mods, though there is a large number of mods common to both. Even within this pool of commonality, Game 2 has updated versions of a handful of mods. The only change I made to game 1 was to replace zaz animation package 7.0 w/ 8.0+. Game 2 started with that (zaz 8+).
I started Game 2 using the Alternate Start mod, recently, but still have many hours into it. The fast travel issue occurred at the same time for both games.
I'm attaching Game 1 logs from right after I tried to fast travel from Windhelm Stables. First I fast traveled from near there, via the console and enablefasttravel 1. The console command is only good for one trip. When I tried to fast travel again w/o using the console, the message appeared and I can't go anywhere except on foot.
Game 1 - vanilla start
Game 2 - Alternate Start
Skyrim Legendary edition.