Oh man that is brutal! I remember my buddy Kevin wore a full Master Chief armor set to a con in Austin back in July and the foam chest piece literally started peeling off his chest from sweat. He had to glue it back on with super glue in the bathroom and it left this awful white stain all over the front. The worst part was the helmet fogged up so bad he couldn't see anything and he walked straight into a pillar. He ended up just carrying the helmet around and telling everyone he was "off duty." I felt so bad for him but honestly we still laugh about it every time we plan a summer con now.

Did you try adding calcium chloride to stop the mush?

Hold up - you mentioned using a split jig made from scrap plywood, but what kind of blade were you running on that 15 year old DeWalt? I've seen guys try to push a dull 60 tooth blade through thick crown and it puts way more stress on the jig than it should (since the blade gets hot and warps, the wood binds easier). Did you check if the arbor nut was torqued down right before you started cutting? That little hairline crack might have been there from a previous cut where the blade wobbled just enough to start the damage.

Actually, about the epoxy primer thing - you gotta be careful there. Modern epoxies are miles better than the old stuff, sure, but they're not a magic moisture barrier if you've got thin filler over bare metal. I've seen guys slap on a skim coat of filler right over bare steel with epoxy on top, and it's fine for a while, then it starts bleeding through the paint a year later (little brown spots, you know the ones). The real trick is you still want to at least hit the bare metal with a self-etching primer or a proper metal prep before the filler, even if it's a super thin layer, just to kill any chemical reaction. Epoxy over filler that's on bare metal can trap microscopic moisture from the filler's curing process, and that's where the problems start in humid climates. So yeah, filler is totally fine for production work, but skip the metal prep step and you're gambling on that $200 holding up long term.

That 1/8 inch drift is exactly the kind of thing that makes you question every cut after it happens... I wonder though, when you clamped the jig down, were you actually cranking it tight enough to flex the plastic body? I've seen guys get that 1/8 inch error just from overtightening a clamp on a thin piece of particle board, warping the whole setup before they even drill. And then a couple wobbly holes later the bushing starts walking around in the oversize pocket and you're doomed from the start. Did you happen to check the face of the jig for any visible bowing or flex when you had it clamped down tight, or was it on a scrap piece that might have been a little curved?