Thank you very much for pointing this out and posting it to our forum. We commonly have this problem with all Raymarine equipment. It is less likely with other devices. We have always believed that it is a manufacturing choice by the companies. We also know that with the voltage changes between RS232 and RS422 some companies change and swap the plus and minus connections around to suit. It would be great if the NMEA standard was always a standard for all companies.
How old is your equipment that you have added to the A031? We also find older equipment requires this reversing.
Please let us know and thank you for getting in touch.
Best regards