Why is my Xbox Series X controller (in Win10) Xbox logo flashing slowly?

This is happening both in wireless mode with the dongle and connected via USB-C cable. I thought it might be do to an update and running the Win10 Xbox Accessories app did net one update but it’s still flashing (but working) incessantly. Any ideas?

If it ain’t batteries or an update, is it properly paired with whatever (Xbox, dongle, …)?

Yes, it’s paired with the dongle (not plugged in now since using cable) and works when the cable is exchanged for the dongle. It’s weird. It’s a 3 state (lit, dim, off) slow blinking.

Seems like it’s still looking for the conection to the dongle you unplugged/switched off? The slow blink is usually the unpaired indicator.