My MKR WIFI 1010 has the same
issue feature others have noted where the CHRG LED will blink at about .5Hz after a few hours.
My board operates just fine despite this and it is mostly harmless, except that an inductor (or some other compnent) used to power the LED is actually noisy. If I'm across the room I don't notice it, but I use the arduino for a home automation device at my desk, and when it's only a foot and a half away from my ear the rhythmic whine is extremely annoying.
I can press the reset button for some temporary reprieve, but I would rather just fix it permanently. I have considered just de-soldering and removing the LED, but I don't want to end up breaking the device. Is there any other, simpler option I can pursue? Maybe disable the battery functionality via software (I don't use a battery)? Or perhaps short the battery charging circuit with a resistor to trick it into thinking it's actually charging something (which now that I type it out seems like a terrible idea)?
If I don't get any replies I'll break out the soldering iron and see what happens if I remove the LED. Worst case I lose a $30 part to science.