"@ Michael B, I only ran into this when I first started running EKF. It was explained that there is a lag with EKF starts running. Therefore the momentary "Bad AHRS" which clears itself.  If it doesn't clear that is another matter (I've never…"

"To keep it "simple" (pun intended) I programmed a separate 3 position switch, on a Taranis, with Normal, Simple and Super Simple. Each have audible alerts. 
SS was the only thing that saved my bird when an Auto Mission went awry. YMMV"

"It is my understanding (and experience) that seeing "bad AHRS" on startup is due to the momentary lag as EKF is starting up (mine always clears momentarily) . I only started seeing it back when I first started EKF logging."

"My past experience (3.2.1) with "Bad AHRS" was only momentary. When using EKF it takes a few seconds for EKF to startup and the error to clear. This is assuming nothing is "really bad.""

"FWIW: you might consider spraying everything with Corrosion X."

"If all is going well you may have a minute or so to spare Autotuning"

"@Craig DeFleming
First Issue: It's takes a few seconds for the EKF to start functioning. The BAD AHRS warning should always clear itself momentarily on the HUD."

"I didn't read the logs, but with the compass failure and 0 sats the PH had nothing to work with in RTL. Analysis reports GPS failure."

"Indeed; I'd rather protect against a potential  problem than have to repair the results of one. Ha"

"I couldn't write a book... but I could read one (big smile, small chuckle).
The groundplane can be a simple as a DIY copper sheet for mounting the GPS.
Here's an article that provides a bit of detail."

"The use of a ground plane has been very effective in reducing equipment noise on other GPS configurations."

"I've found the more I've taken off and flown in Stab the less I think about the 50% rule when switching modes. My "thumbs" just know it's a manual mode.
Best,SC"

"1- I've experienced some great Auto landings and some delayed disarms as well. I am quick to switch to Stab when there is any delay. Sometimes I switch to Stab a bit before landing to remove all doubt."

"I don't have experience with the external XJT.  If you don't get some quick help here you might take this up with the Taranis guys"

"Did you switch to D16 in the radio yet?
SC"