Switch, Battery wake up and sleep on its own

[Rotary]

Hey,

I have a strange problem with a Switch, unknown history.

When power up it shut down at the Nintendo logo cause of drained battery. Put it on working charger but switch stuck at 1% for hours. After disconnecting the battery from the mainboard and hook it back again, no reaction at all. Not even the battery icon when connect the charger.
I tried to boot hekate which worked. Battery info showed 1000mA for design battery capacity with a !
Let it charge to 100% and drain to 0%. During Charge again, suddenly hekate showed 0 on alle values and locked up. After reboot it seemd to boot normal to OFW and charged to 100%. After reboot, black screen again and no battery icon when charging.
Boot to Atmosphere works, but randomly there is the big battery empty icon over the whole screen even when you can recognize actuall battery state which is now 97%.
Screen goes black, after a few seconds screen comes on by its own, shows 97% goes darker a few seconds later, then becomes black. Few seconds later comes on again, showes 97% followed by the big battery empty over the whole screen, goes black. This repeats on and on.

Any ideas on this ?

[coda]

do you have another known working battery to test with?

[Rotary]

Yes, already tried with a known good battery, Its the same.

here is shown how it behaves

later when its on the charger it stayed on. When i had a look in the controller menu, i have seen this…

I found a right Joy-Con rail where the contacts look like after a battery acid accident. Switched the rial to a new one and it dissapeared for the right one. After switching the left Joy-Con to a knowen good, it stopped (the fraking out battery indicators) and the console stayed on.
Tried to reboot to OFW and it worked. At the moment 10 out of 10 boots to OFW worked, so it seems it was the coroded rail and a defective Joy-Con.
Btw. this freaking out battery icon for the left Joy-Con is happening on a good switch, too. So definitly somethings wrong with it.

[Rotary]

Suddenly it fall back. Its nott booting in OFW, Atmosphere no problem. It was not charing the Joycons then in battery mode. When plugging in the original charger, the joycon started immediately to charge and keept charging when back to battery mode.
Next try for OFW, and it worked again. I don´t get it.
sounds a bit like power distribution !?

[Rotary]

OK !? now it becomes completly bonkers. I can reproduce it now. The Switch only boot when a left Joy-Con is snapped in its rail. When its released and and no connection it stays black.