Homerunner /create intermittently fails with "failed to create deployment: CreateDeployment: Deploy returned error"

[Half-Shot]

failed to create deployment: CreateDeployment: Deploy returned error Deploy: No images have been built for blueprint my_blueprint_name_12345

It seems to happen on and off, I can't seem to nail down why. The request body looks like:

{
        base_image_uri: `complement-synapse`,
        blueprint: {
            Name: `my_blueprint_name_12345`,
            Homeservers: [{
                Name: hs_name,
                ApplicationServices: [as_registration],
                Users: [{localpart: "foo"}],
            }]
        }
    }

[Half-Shot]

This was dramatically improved by bumping the value of HOMERUNNER_SPAWN_HS_TIMEOUT_SECS from 30s (default) to 50s.