I don't know what I can say. I'm using FULL STOCK android 8.1 directly from Google, only rooted. I've just tried again and no luck. Stickmount mounts the device to /sdcard/usbStorage/128gb but I can't set that path. The path browser won't let me get higher than /storage
So I can't set the path manually.
If you can tell me what I need to do manually to fix this I'd be happy to try it.
New log attached
Sent from my Nexus 6P with Tapatalk
E *MX.Directory: Can't open directory '/storage/emulated/0/usbStorage/128GB'. errno=18