I just had to have my Lumia 950 replaced under warranty yesterday, after hardly having the phone for a week. There was something wrong with the charging circuit that was preventing it from reliably connecting.
For the most part, whenever I plugged a charger into the phone, the phone would not start charging at all. During some additional troubleshooting in the store, while I was there for the return, we got the phone to respond a little but the charging indicator would not stay steady.
What we were seeing (whenever the phone would register a charger connected) was that the phone would say it was charging, but the power plug next to the battery icon would blink on and off. We didn't test it long enough to see if it actually was charging, but we did look at a display model for comparison. (In fact, we were borrowing that unit's charger for the test.) When the display model was charging, the plug would stay steady.
Last night, I had some similar issues with the phone. It was very slow to charge, and the power plug on the battery icon in the Notifications area was blinking again. (To be fair, I was running some apps that are known to drain the battery heavily. But the slowness to charge persisted for awhile after I'd shut them down, and the plug still kept blinking.)
Today, I think the phone is charging okay (haven't really watched it long enough to tell yet) but the plug is still blinking when it charges.
Is this normal? What are the various states of the power/battery icon for Windows 10 Mobile devices, and what do they mean?