I've run into this issue trying to use react-native-360. I realize it's no longer maintained, just hoping it jogs someone's memory are they could:
__44-[RCTUIManager flushUIBlocksWithCompletion:]_block_invoke
RCTUIManager.m:1201
__44-[RCTUIManager flushUIBlocksWithCompletion:]_block_invoke.498
__RCTExecuteOnMainQueue_block_invoke
_dispatch_call_block_and_release
_dispatch_client_callout
_dispatch_main_queue_drain
_dispatch_main_queue_callback_4CF
__CFRUNLOOP_IS_SERVICING_THE_MAIN_DISPATCH_QUEUE__
__CFRunLoopRun
CFRunLoopRunSpecific
GSEventRunModal
-[UIApplication _run]
UIApplicationMain
main
start_sim
0x0
Pods installed, RNGoogleVR dragged into Xcode. Builds fine.
React Native 0.68.2
GVRSDK 1.170.0
Thanks @tiero and everyone else who reads it