Autopilot flies away

[wings_level]

So I had this strange incident today with my Stec 30 Autopilot.  About 45 minutes into my 2 hour flight the autopilot was tracking and holding altitude like it normally does.  Then, out of no where it decides to take a huge deviation.  Flying a heading of say 010, all of a sudden it starts a standard rate turn about 90 degrees right.  I just sit there and watch it, curious as to where it wants to go.  I let it fly this for about 7 or 8 miles off course before I realize it’s not going to correct itself.  It never changed altitude, just track.  I then turned the Autopilot off and hand flew it back on course.  Once back on course, I powered the autopilot back up, and engaged the autopilot to follow the gps track and hold altitude.  Then after a few minutes it would begin to oscillate, chasing the magenta line.  Heading of 010, it would turn to about 016 then overshoot the course by .25 to .5 miles, then correct itself to a heading of close to 360 and overshoot again.  This went back and forth and never settled in on tracking the line.  Anyone ever heard of this phenomenon?

Edited November 30, 2021 by wings_level

[EricJ]

The electrical output of your DG may have died, or lost connection to the AP somehow.