Asset Tracker Electron board's red LED sometimes blinks really fast

I have 2 asset trackers sitting here.
Both have a GPS fix. GPS shield red LED is off.
Tracker-A’s Electron board’s red LED is flickering continually.
Tracker-B’s is sold.
Both have same firmware.
Neither has battery.
Each Electron is outputting debug messages to USB serial ok.

When I plug battery into Tracker-A, flickering red LED turns off.
When I remove battery, flickering starts.

Actually the behaviour of device A is the intended behaviour. B is odd tho’

However there is a thread that shows how to turn the charging LED off for good.

I just configured my 3rd Asset Tracker Electron.
Electron’s red LED blinks fast if no battery.
I install battery, red LED is steady on.
Disconnect battery, blinks really fast again.

My 1st and 2nd AT Electrons have fully charged batteries and no red LED.

Separate gripe:
But they are both blinking blue, so I’ve given up on them and am moving on to new AT Electrons.
(thanking self for purchasing 3 more last week, so I can remain productive this week)

As said earlier.
That’s normal amd should be the case on all your other Electrons too.
That LED is the charging indicator which is lit while charging and without LiPo it permanently tries but fails to charge, hence the rapid blinking.

Blinking blue indicates issues with the SIM.
Are they Particle or 3rd party?
Are they installed correctly? (try fitting them again)
Have you activated them?

BTW, in you initial post you mentioned A behaving the same (correct) while B was not doing the red flashing although it should have. Has B started to behave normal then (LED off with fully charged battery installed)?