What could be causing this discrepancy between boards?

[LoveLaika]

I built a DC switching power supply that takes in a positive DC voltage (~+14 volts, 3 amps) and outputs both a positive and negative voltage with a buck and an inverting buck-boost configuration respectively. After running simulations on it, I ordered the board and components, laid it out, and it works. It really works with dummy loads of power resistors as shown in the schematic. Compared to my previous supply, the goal was to mitigate the inrush current as well as provide flexibility as to when the positive and negative voltages would reach their peak.

After building the first board and verifying that it worked with 20-ohm loads at both positive and negative output voltages (~500 mA each at a +10/-10V output), I went to build another board. However, upon building the board and powering it up with no load, this board was shorted. Troubleshooting revealed that the problem was the negative voltage regulator IC. It was somehow causing a short between the power input for the ICs to the board's ground plane.

After replacing the faulty chip, the second board was no longer shorted and could output voltages, but the negative voltage regulator side could no longer handle a 20-ohm load. When a 20-ohm load was attached, the output voltage only went to -3.1 volts. The positive voltage regulator side could maintain +10 volts with a 20-ohm load, so there seems to be no problem with that. With no load, the board was outputting +10 V and -10 V, same as the first board. (Strangely enough, the negative regulator could output -10 volts with a 27-ohm load, so I don't see why 20-ohms would not work). I tried replacing components such as the regulator ICs, the inductor, and the capacitors, but to no avail. This phenomenon is really strange considering how the first board worked fine. It also occurs when the positive voltage regulator is disabled (so all of the current being drawn is from the negative regulator). Can anyone help me with possible thoughts as to why this is occurring?

[SiliconWizard]

Have you looked at the transient of the negative output (relative to GND) when powering on the board (at no load)?

[LoveLaika]

Not too closely. Using an oscilloscope, I observed that the negative output reaches it desired value after roughly 380 milliseconds. I did observe some low amplitude ringing as well, but that was done looking at the signal as an AC input.