Hi. Testing mods to start a new game, i discover than the area of north forest is accesible in charpter 2, not in charpter 6. The only mods installed are tob-ex v28, bg2fipack v13 and bp-bgt-worldmap v13 in that order.
Digging if this can be solved, i found only with certain configuration happen this problem, specifically when you choose in the options "original travel times and area visibility" in the bp-bgt-worldmap installation. Not happens when you select "revised travel times and area visibility", and definitely doesn´t happen if this mod is not installed.
Tested in windows 7 and 10. The bug is present in versions v10.2.1 to v13 of the bp-bgt-worldmap i think (i tested only those two versions).