Yep - correct,
Planking is caused by the timber on the PF shrinking and expanding ( either way).
Yours has shrunk causing the artwork to crack and raise as the two sides push against each other.
How you tackle it depends on how bad it is, sometimes you can tape either side of the line and rub back to smooth then touch up.
If you CC then rub back you have to keep doing it till youve built up enough CC to cover the raised cracks... can be quite a few coats and sometimes heavy CC looks odd.
If its in one area then you can stencil off to a black line and just CC that area, rub back etc... saves doing the whole PF
