I’ve got new supplies and tools in hand, but have not yet done anything with them. I’ll get motivated soon. 
In the meantime I just noticed that this driver also uses the QX5241a: 9A 3-Mode 5.5-12V Circuit board. HKJ wasn’t super impressed with the efficiency, but hopefully better component selection will keep us around 80%. RMM comments that most XM-L2’s seem to die around 4.15v over here (post #110), so we can see from HKJ’s scope traces that depending on the input voltage this thing would totally zap XM-L2’s. HKJ didn’t specifically mention the input voltages, only that the two traces were at different voltages.
EDIT: I forgot to mention that those scope traces (the pictures with green lines that look like wiggly square waves) look exactly like what I’ve been seeing.