VCC rail rising at 4.6V in some code-specific conditions...

Hi guys,

I ordered a few days ago 2 Espruino Pico from Tindie, and yesterday I came accross some very strange behaviour/bug (?!?) : When I run this code on the Pico (revision 1v75), the VCC rail (usually 3.3V) raises up to ~4.6V, which seems to be approximately the same voltage as VBAT.

" Serial1.setup(4800);
Serial1.on('data', function (data) { print(" "+data); });
Serial1.print("hello"); "

I checked the hardware, no visual damage. The solder pad which is meant to control the battery Mosfet with B0 is NOT soldered.

Using Serial2 instead of Serial1 avoids this behaviour, therefore I suspect a software bug related to Serial1. Furthermore, this bug appears on both Picos.
Any ideas?

Thank you!