Can't use Meta XR Simulator with Effect Mesh building block. OverflowException. v77 with Unity 6.

Alright, so I didn't manage to solve the core issue, however I did manage to get a JSON recording out of the headset, but it doesn't work at all since the room geometry is not entirely correct (only floor, walls and ceiling are correct, rest is garbage), and it still crashes with an overflow exception while using the Effect Mesh.

For anyone interested:

• I discovered that the SceneDataRecorder.apk was located in C:\Users\my_username\AppData\Local\MetaXR\MetaXrSimulator\77\data_recorders
• For it to work, after installing, I had to give the installed SceneDataRecorder app write permissions, and spatial data permissions. On your headset, go to settings > privacy and security > app permissions > spatial data, storage.
• After launching SceneDataRecorder from unknown origins, and scanning my room, a file appeared at the ROOT of the device storage, not on sdcard > android > data > com.oculus.vrshell, but on the root path (sdcard). File name is scene_recorder_out.json
• I extracted this file using SideQuest to my computer. 
• Then, I renamed this file myroom.json and put it on C:\Users\my_username\AppData\Local\MetaXR\MetaXrSimulator\77\config
• There, I found 2 other JSON rooms for testing

Now, for running these JSON files on the Meta XR Simulator:

• In Unity, go to Edit > Settings > Meta XR
• In Unity go to Meta > Meta XR Simulator > JSON Server > Launch JSON Server
• A file dialogue will appear, go to C:\Users\my_username\AppData\Local\MetaXR\MetaXrSimulator\77\config and select one of the JSON files
• Press play

So, this launches the selected JSON room, however for me it still crashes with an overflow exception if I have the Effect Mesh block enabled.

I really wish Meta would at least update their docs.