I have been working on a VTOL modification for a couple of weeks now, and had just gotten to the point of conducting a few hover tests. The night before I went through and checked to make sure everything was properly functioning, and all was well. On the day of the test however, I began running into issues. At first, the ESCs started giving the error beeping tones on two of the motors; however, after unplugging the ESC from the battery (Turnigy 5000 mAh 4 cell) and Pixhawk and reconnecting them, all was well. I then went to go run the flight test, and one motor began spinning with much higher thrust than the others. The day before I had checked these and the limits were configured. To resolve this I simply reconfigured the limits. Now we get to the interesting part. After these issues were resolved one of my ESCs stopped sending power through the BEC, and would not emit any startup tones in the motors. I attempted to reprogram it with the use of a program card, also to check to see if it was sending signal to the motors, which it was not. This started with just one ESC, but has now affected a total of three. I can't seem to understand what the issue is. Any ideas or help would be greatly appreciated!