I'm getting a similar issue with an accompanying runtime error. Only started happening in Act 2 as well. Interestingly, the error pops up at the start of a loading screen but doesn't prevent the loading bar from continuing - until it gets to around 80%. Then loading freezes there completely.
You guys are welcome to continue trying to look for a solution but I've tried damn near everything and absolutely nothing has worked. Don't get too frustrated with yourselves cause this issue is happening to a lot of people and it's definitely just a problem the devs need to sort out.
