I have a Squier jazz that showed the same symptoms, altough it took a few days to bow.
I realised the end ancor of the rod was moving, crushing the wood.
It is, luckily, headstock end adjustment. I took the neck off expecting to have to drill into the back of the heel to find the anchor, but the skunk stripe was about 5mm short and i could see the anchor in the gap.
My kill or cure remedy was a cc or two of cyano acrylate into the hole (with truss rod slacked right off). The idea was to strengthen the wood where it was being crushed, not to glue the truss rod in place. I also added a washer under the nut to restore the full range of adjustment.
I gave it a day to set and readjusted after a week. Since then over two years I have made a couple of minor adjustments, including slacking off so it seems to have worked.
Not sure how you would do this with heel adjustment. Drill a hole and then plug it? Its pretty drastic, but as a last resort?