47-55.1 carboard headliner distorting

[leegreen]

I recently installed a repop carboard headliner. Got it in with no issues and if fit well. Fast-forward a week of sunny weather and we just had 36 hours of rain.
Now the headliner has got some bulges and dips. My truck does not leak but I did get in and drive with damp clothes a couple times

Anyone else had that experience?

Curious to see if it flattens out again with dry weather. This carboard one may just become a template to cut some out of fiberglass or something.