Github payload unmarshaling failed for Push event

[hugoeeb]

Using image v0.2.79.

When making a push on Github, the delivery has the green checkmark and "looks" successful, but in the background, the proxy is getting this log:
Github payload unmarshaling failed for Push event: invalid character 'p' looking for beginning of value

Content type is set to application/x-www-form-urlencoded
If I try json instead, it's returning log: Error Validating Hook: <nil>

Any idea on what could be causing this?