Matek405wing bizarre servo behavior upon radio shutoff

I have matekf405 wing FC in AR900 wing . This has flown before , about a dozen flights . I’ve never went so far out where my radio link failed .
On the bench I just discovered that when I shut off my transmitter the servos go nuts , jittering all over the place . When and if they settle down the wing ……which is level on bench in STAB mode …… places elevens in a hard left roll position and keeps them there .
Does this mean If I fail safe in field the wing will spiral into ground instead of RTL ?
Also I notice sometimes I have to disconnect and reconnect power several times to get the FC to initialize . That never happened before .
I’ve tried both analog and digital servos , no difference . The flaky behavior is being commanded by FC .
I recently installed analog airspeed sensor , have not flown it yet . I already tried changing all the airspeed sensor settings back to that of a board without one , no difference .
Arduplane 4.0.9 firmware .

Just to be sure, plug in mission planner before you shut off the radio and see what happens. Your plane should be going into RTH, but because your on the bench probably right on top of the home location, the GPS noise is confusing the FC as to what direction home is from the plane and the servos are reacting. As long as you verify the mode change to RTH you should be okay.

I have exactly the same setup, AR900 with Matek 405wing, and it does the same thing.

Ok that makes sense . I figured I’d ask before I crash .
Do you get twitchy servos sometimes , only in auto modes , manual is fine .
The servos jitter sometimes even with transmitter on , just nowhere near as bad as when tx is turned off . Other times the thing is dead still until you move it .
I have noticed a relationship between how far from perfect level the wing is sitting after initialize and the amount of jitter I see .
In other words I can induce more jitter at startup if I deliberately set the wing at some angle away from level , either pitch or roll .
If I really pay attention and level it good on the bench before startup I see the minimum amount of jitter or none at all .
Maybe nothing ?
Anyway thanks a lot for info.

Yeah, you will get some movement of the servos. Modes like FBWA&B don’t really care if the plane is flying or not. If it’s not level (or the commanded attitude) the servos will move to make it happen. And depending on your tuning they may be a bit twitchy. I’ve been noticing that as I get my tuning dialled in better they are less twitchy.

At start up with all my planes I am just in the habit of having them sit (reasonably) level on the ground or a bench. And I try not to let them move until all the initializations are done. It’s probably a bit of overkill but it’s just my habit and it seems to work for me so why mess with it.