'Magic smoke' due to wrong powering of Navio2

I’m building a custom drone with Navio2 + RPi3 and had to switch from the bundled power module to another one for placement and weight reasons. Everything was OK until the power cord suddenly disconnected from the PDB. It’s 2 pin 2.54 mm connector. When reconnecting, I’m sure, I didn’t swapped the polarity, but obviously connected it the wrong way (maybe plugged to wrong pins), so after connecting the battery the “magic smoke” went out of somewhere in my setup. I quickly checked, that RPi worked fine, but Navio2 doesn’t work now (LED is off, I2C scanning with i2cdetect takes so long, no sensor can be found and the board itself getting so warm right after switching it on). I assume, the power supply circuit is damaged. Still there’s no any visible defects on Navio2, no burnouts, visually damaged components etc. So my question is: before taking any major measures of replacement or switching to another FC etc. I just wanted to ask if maybe someone could suggest any quick and common cause for such a problem, which I still can fix to get it working again?

Magic smoke is a tough one. It is a toss up as to where the leak came from. Even harder to get the smoke back in the hole it came out of. Good luck.

Yes, indeed, thank you! As a quick solution, trying to switch to my another working BBB-mini for now. As you’ve mentioned, there’s a little chance I can fix or restore Navio after this.