UE 4.21.2 fatal error on packaged build

I’ve been able to package and test builds with UE 4.20.2 for weeks, but as soon as I updated to 4.21.2, I can’t launch my game anymore. Editor play works fine, standalone game option works fine - it’s just the packaged build that’s an instant fatal error. I’ve rebuilt every map, looked through settings, and tried any fix I could find but nothing. It might be my Niagara plugin but I’m not sure how to fix it besides completely removing it from the project (really don’t want to!)

I also have red text pop up in my output log frequently that reads, “LogRHI: Error: GetAndOrCreateGraphicsPipelineState RenderTarget check failed with: 480 !” Sometimes it goes away, but I don’t know what the cause is.

Here’s the latest crash log that I have: UE crashlog - Pastebin.com

Any help is greatly appreciated.

I also can’t package 4.21.2, but my error looks different.

UATHelper: Packaging (Windows (64-bit)): LogWindows: Error: Fatal error: [File:D:\Build++UE4\Sync\Engine\Source\Runtime\CoreUObject\Private\UObject\UObjectGlobals.cpp] [Line: 305]
UATHelper: Packaging (Windows (64-bit)): LogWindows: Error: Illegal call to StaticFindObject() while serializing object data!

Does it looks like this by any chance?