I am Done with the 1040

Sad to hear that you are having so many issues with the Edge 1040 .
I know it could be a lot better, Garmin should work on their test cases. Each release has new bugs, some annoying some very small.

On the other hand:
Today I rode over 100 km with navigation, connected with an RTL Varia radar, 4iiii power meter, Garmin HRM dual, Garmin speed sensor and Shimano Di2 12-speed. When I stopped at home the device synched with my Samsung S23 and uploaded the file to Garmin. No problem at all. Most rides go like this
(two days ago the device rebooted during a ride, very annoying)

Maybe you just have a faulty device.

My radar drops out multiple times every ride.  Most of the time it reconnects but it's still frustrating that you pay a lot for ALL Garmin equipment and the Garmin equipment doesn't play nicely together.  

Garmin Edge 1040 can not reliably gauge speed when I'm on a street with lots of trees. So I have to get the Garmin speed sensor which drops or never even connects on some rides.

The software updates are mostly a joke. However, getting rid of that music at the top of every climb was the best mistake they ever fixed!

I completely agree with your opinion - Garmin has become a complete *** and I am very sorry that I also changed 830 to 1040. Garmin has never seen the worst experience of the system's user interaction and technical support. Every day presents surprises... now I have made a plan for the week, everything is ok in the calendar on the phone, for some reason it offers its own plan on the device, which I do not need for nothing. 

My radar drops out when it gets overloaded by a traffic light radar. Solid otherwise and no ANT+ problems generally. Does sound like OP has a faulty unit.

My experience matches yours, Rob. It's mainly temporary traffic lights that cause the dropout issue for me.

I share your feeling. I am experiencing more and more ANT dropouts. Yesterday all sensors (HRM, Di2, Rally pedals, Varia radar)  connected before my ride, to show no data after rinding 50 meters. I have to turn the device off and on again to get ANT sensors back. Very annoying...

My experience was similar when I had an Edge 1040, and even worse on my current 840. (which I suspect is par for the course as they probably share a code-base)

I've owned dozens of Garmin watches and fitness trackers - the Edge x40 series are the buggiest devices I've ever owned. Frequent ANT+ connectivity issues (with Tacx trainers, Garmin HR straps and Rally pedals no less, not even third-party devices), as well as inconsistent behaviour with the Varia RCT715 and Bontrager ION lights.

Device crashes and restarts while navigating are common.

I've done the suggested hard-reset of the device and set it up from scratch. That seemed to make things slightly better but nowhere near acceptable.

Agreed! My Varia radar (connected via ANT+) is constantly disconnect and reconnect throughout the ride. The most annoying thing is each time it disconnect and reconnect, it makes a beeping sound. Imagine my 1040 constantly beeping throughout a 2 hrs ride. 

I have encountered the Varia RTL 510 frequent disconnects too.

It is just frustrating regarding astronomical price we pay for that devices.

I can agree that the 1040 has been a bad. For me It took almost a year before it worked as it should. Also the support from Garmin to solve my problems was absolutely terrible. 

Adding that all problems on 1040, worked just fine on 1030. 

For a couple of months it has actually worked as it should, but not a happy customer