connectivity issues with both Ethernet & WiFi

OK. This is has been a problem for me for some time now. MacBook Pro Retina mid 2015 model. I resolved that this laptop was no longer reliable. So, I got a new one and placed this mid-2015 model on the desk. I started using it again last year in a place with no wifi. So I’m using an Apple Thunderbolt to Ethernet adapter (https://www.apple.com/shop/product/MD463...). After a year of using it with no problems, I thought that maybe some update fixed. I moved the computer to a new location, unplugged to adapter, and connected to wifi — and — the computer started shutting down after a few minutes. Now, I’m using it on wifi with the adapter dongle in a thunderbolt port and no problems. It may be a fluke — but — seems to be working. It doesn’t matter what port it’s in.

I don’t know if this works for anyone else, but maybe it just might point to the underlying problem.