So First off, I flew the other morning down to the Seattle mode c ring to confirm my suspicion that the issue is local radar interference. We have two maritime shore based radar stations here and I noticed the mode 3A failures occurred near them as well as on the ground. The report for my flight today showed zero errors. It seems my mode c is hit and miss on the ground (today luckily it was hit), probably a product of marginal reception of the nearest atc facility.
I received an email also the last week from the FAA guy stating they are investigating the following issues and that I should fly as normal until they get it figured out. They acknowledge there is an issue with mode 3A errors with the Skybeacon such as when the aircraft is on the ground in a non-coverage area and the transponder isn’t being interrogated, and yes, you will fail a test flight if this happens, they don’t care that it wasn’t in “rule” airspace. They are working with Uavionix engineers on this issue. The FAA guy also indicated they need to have an internal meeting and determine what an acceptable level of performance is outside of “rule” airspace. This confuses me since it isn’t required in those areas. He said he would advise me when they have determined this.