Strange Map Glitch
You weren't "randomly transferred to another map". The border of Peregrine transports you to Talos Island. That part is intended. In fact, back before Ouro was released, a quick shortcut from Portal Corp to Talos was to head East toward the border. It was quick and convenient.
Usually, you'd be placed at the Ferry in Talos, but since the last issue, it seems to be broken. As you have found out, it sometimes brings you a location outside of the War Walls instead. I've bugged it and a few other people have made similar threads about it as well.
I'm sure it'll be fixed Soon™. lol
So at one point tonight I found myself randomly transferred to another map, outside of the barrier wall. There was a Rikti invasion in Perigrine Island and for some reason I decided to start chasing after one of the dropships. I had my jetpack on and was flying north away from the main island after it, blasting away until suddenly I hit a load screen. Afterwards, I found myself in the far north section of Talos Island, in the empty space beyond the shield wall. Just to see what would happen, I turned off my jetpack and fell far enough to damage me down to 1 HP. I was able to walk under the city (miles under the city) until I eventually flew back towards the shield wall and was somehow transported to the plaza in front of the train.
Just thought I would share this strange experience with everyone. Not that it's anything that really requires any immediate attention since I think it would be pretty hard to recreate the situation lol