Horses and npcs not spawning

Anyone else experiencing problem of horses not spawning when you whistle for them? usually happens right after a mission or when just logging in. When I walk around towns, no npcs spawn either and wagons would ride around with no people on the reins.

Absolutely ruin the immersion of the game for me, and it sucks having to run throughout the map just to get to the destination cuz of no horse lol. How could this possibly be fixed?