Had a problem from a customer the other day. The batteries in his garage door left open notifier were getting drained really fast, like in a week. The batteries should last a year! We dug into it and found the problem: a solder bridge on the U2 voltage regulator.
I pulled out the nodemcu and checked voltages with a fresh set of batteries. I checked the voltage on the header at the spot where D4 plugs in, and it was reading 4.5 volts, which is way high. It should be 3.3 volts. That pointed to something strange with the voltage regulator U2, which feeds the holtek. Visually inspection showed that there was a solder bridge between the input and output pins of the voltage regulator, so we removed that. Checking again after it was out showed there was still a bridge on those 2 pads. Scraping around those pads fixed that, but I was worried that putting a new voltage regulator back in the same spot would just recreate the bridge. To avoid that we jury rigged it, and I was so ashamed of the outcome that I didn't even take a picture to put on this blog post ;).
Testing showed that it was back to 3.3 volts on the D4 pin spot which was a good sign. We assumed it burned out the D4 pin, so we replaced the NodeMCU with another one and it worked good as new!
To make sure that the board is assembled correctly, I added some more info to the Hardware Assembly page, it now shows how to verify the operation of the U2 voltage regulator: