powerboost shield 500mA appears shorted

[socrates1024]

I'm having a problem with a powerboost shield 500mA that arrived this week. Order number is 2520755-0759996712

After using it just fine for 20 minutes or so, it stopped working. It behaves exactly the same way as reported in this forum post viewtopic.php?f=31&t=174843&p=852912&hi ... st#p852912 ....
basically when powered by microUSB the charging light is on but otherwise no functionality. Based on the discussion in the linked post above, I confirmed with a continuity checker there's a short across VBat and Gnd. I don't see any reason my downstream project (I stacked it with a servo shield and a metro from this order) would have caused this.

Attaching photos of my soldering

[Franklin97355]

Soldering looks good. What battery do you use and, if it was not an Adafruit product did you confirm the polarity?

[socrates1024]

Thanks for the reply - I only used the 1200mah 3.7v battery that came with the powerboost shield

[Franklin97355]

Sorry for the delay. Contact [email protected] and we can replace the shield to see if it is actually shorted.

[socrates1024]

The replacement powerboost shield did the exact same thing after attaching it to an adafruit metro.
I observed that it was making a humming/whining sound while running on the battery prior to the light going off and then acting as described above. I don't know if that gives a hint as to what could be going wrong?