I think my son's 99 was done with Panel bond. Within the pile of reciepts he got with it was proof the PO bought panel bond for it at least 3 different times. and now (I dont remember how long before my son bought it that the truck was redone) but hes had it ~3 years and it looks like absolute [censored]. the patch panels have rotted out again over the wheel wells and you can see the parting line between the patch panels and teh parent metal like someone drew them with a rust colored Sharpie. the truck is white and it really stands out.

When I have done patch panels in the past myself Ive always flanged the parent metal and cut the patch to fit within the flange and welded it up a dot at a time. Most recent was pass side rocker on my 96 Dakota. took about 2 years for the seam to show as a rusty outline.
Yet probably 30 years ago when I did the cab corner on my 79 D150, and done the same way, it never did that and I had that truck 4-5 years after putting in that cab corner. that's why I thought it must be something with dissimilarity in the grade of metal originally used vs what patch panels are now stamped from.