How to rollback firmware

Create an empty file named force.tmp, copy this file and gupdate.gsp to the Garmin directory. Restart the device.

Thank you so much for this instruction. It is of great help now I am at the start for 6-week bicycle trip. After using Garmin navigation for decades, I think Garmin has become very close to a point of no return for me to switch to another brand, like Wahoo. But thank you very much for your help, that has saved my Edge at least for the short term.

Have you tried s factory reset before downgrading?

my 1040 is on latest beta, too and it is flawless.

Yes. Each time I install a new update, I hard reset the Garmin. After long time experience with Garmin's udate policies, hard resets have become a habit for me after each update. Like I did this time after downgrading from beta 27.09 to 26.17

For my tasks, training up to 100 km, 27.09 works fine, does not reboot. Did a reset, uninstalled IQ apps, deleted all tracks, workouts and activities. So far so good. But the thought of Wahoo is haunting me more and more often)

Just a note on this, it's important to share your error/debug logs of you're in the open beta, this is how the issues get diagnosed and resolved. So before rolling back, do share your logs via the usual safe upload process. 

Secondly, I had also done a full factory reset before giving up (and before a race I needed a working computer for), so only as a last resort given the circumstances did I do the rollback. 

I don't understand why many user HAVE problems and many users DON'T.

On the same beta.

Because different people use the device differently. I had 3 consecutive workouts with no problems with the device on fw 27.09. Yesterday installed the WindField app and after saving the activity the device rebooted 2 times

I use the windfield app for months now, never had a problem