I wonder why you didn't try check yourself. Anyway I test it a bit and the results are very negative:
- Quit and reload a game never change the gremlin towers.
- Change an area like from Verlon to Greenwort and Arlania seems also not change the gremlins towers. About 10 tries in different area with quit and reload or just reload. Not a proof but a clue that it's not area changing that changes gremlins towers.
Character level change could be a reason of Gremlins towers change but that's more difficult to test.