Macbook Air M3-Two Apple Thunderbolt Displays-one display turns off randomly-SOLVED

I've used an Apple Thunderbolt Display (#1) since buying it new in 2013. On several USB-C macBooks I used the Apple Thunderbolt-USB-C adapter.

In October 2024 I bought another Apple Thunderbolt Display (#2) used on Facebook Marketplace. The Apple Store told me I needed two Apple Thunderbolt-USB C Adapters to connect both monitors, so I bought a second adapter, and connected each display to the Macbook Air M3 through its own Thunderbolt adapter.

For one eight-hour day #1 and #2 worked perfectly, through multiple Zoom calls and YouTube sessions. On the second day, #2 started shutting off randomly. I swapped all combinations of monitor-adapter-port, confirming that the problem was with #2. I shot a 17-minute video on my iPhone showing #2 shutting off multiple times.

Then I connected #2 to the Thunderbolt port on the back of #1 using a stand-alone Thunderbolt cable. Problem solved. I have two separate displays with separate content, NOT mirrored. Apparently there is a problem with the Thunderbolt connection/chip on the built-in cable on #2. Wondering if the party that sold it to me knew this....

Problem SOLVED.