undefined is not an object (evaluating 'm[b]')

I get in Swaggerhub errors "undefined is not an object (evaluating 'm[b]')" that I can't explain.

Can you please tell me what could be wrong with the specifications that could cause this?

I tested the specs with swagger-cli validate and with npm run oas:lint (https://github.com/stoplightio/spectral) and they don't give any error or warning.

Steps to reproduce:

1. Open https://app.swaggerhub.com/apis/VNG-sandbox/Waardering-onroerende-zaken/0.1.0

2. In the right pane click the caret to open component "WozObjectHal"

3. Now the code pane shows 6 errors "undefined is not an object (evaluating 'm[b]')", all at line 0.