Wio LTE: errors showing in debug output

I have just started checking out Wio LTE. But I find basic sketches from the examples do not work. When I enable debug mode it indicates errors are being reported by the modem in responses to Specific AT Commands.
Problem is the error messages are gibberish. Just an error number and incomprehensible text describing the error, which does not lead to diagnosis of the real problem.
Please can Seeed publish a document describing in detail the error codes issued by the modem so that problems can more easily be diagnosed (and leading to a solution).