DGK, what Thunderport to displayport adapter are you using?
I had the 1-4 error with an adapter that wasn't compatible, or if I disabled the Intel GPU.
Below are the adapters that I have that does not give the 1-4 error:
Cable Matters USB C to DisplayPort Adapter (USB-C to DisplayPort Adapter, USB C to DP Adapter) Supporting 8K 60Hz Black - Thunderbolt 3 Port Compatible with MacBook Pro, Dell XPS 13, 15 and More
Model 201016-BLK-N
and
Cable Matters USB C to DisplayPort Adapter with 8K HDR DisplayPort 1.4 - USB Type C and Thunderbolt 3 Port Compatible with Oculus Rift S, MacBook Pro, Dell XPS, Surface Pro and More
Model 201086