Big surprise today. I was late into a 3 hour flight in the Milviz C310 using the TDS GTN750xi with Bert's great mod (thank you Bert) on a flight plan in NAV/GPD mode and had been following it nicely, without fail,  at 11,000.  I came up on another slight turn nut the AP kept me going straight.  It drew a segmented magenta line to an airport that was not in the path of my flight plan. Nothing I could try would get me back AP guidance on my flight plan.  I worked with it for likely 45 minutes attempting to determine what was happening, and why.  Never did.  MSFS finally gave up and I got a CTD.  No wonder after all the interactions I made.

After the flight I researched the GTNxi and found it has a Smartglide feature that can assist a glide to an airport in the event of an engine failure.  I did not experience an engine failure.  And I could figure no way to overcome the mode if that is indeed what took over. I later found the page on the GTNxi.  I expect that after it is activated it can also be shut off but I did not find the page.  What an experience.  Have no idea how I triggered it.  Likely a keystroke combination I was reconfiguring a couple of yoke buttons to adjust my Custom Cockpit views.

https://www.youtube.com/watch?v=y3idMj6s2XE&ab_channel=GarminAviation

Nice feature, but big unexpected surprise.

Edited August 26, 20223 yr by fppilot

Yeah it should show up in yellow on the lower left bottom of the gtn if you were in that mode.  Might have accidentally triggered it.  But you can go to the smart glide menu (might be under emergency not at my pc) and deactivate it.