There can be several reasons why this tunnelling of the vinyl appears.
I believe that the reason is most often shrinkage of the vinyl while on the roll or the shelf-life expectancy of the vinyl has passed.
When the vinyl is on its core it is wound pretty tight.
The shelf-life of vinyl is normally 2 years.
Over this period of time, the vinyl will shrink. it’s not visible as such, but if you look closely at the edge of the roll you will see a millimetre or two of the white liner exposed. You can sometimes see this on swatch-book samples also. Obviously, this will happen more with cheaper monomeric vinyl but happens with polymeric too, as well as some so-called casts!
Sometimes it’s not just the “time spent on the roll”, but the room it has been kept in. if you have a room that’s hot all day and cold at night. the vinyl is exposed to this varying temperature every day and again, has an effect on the vinyl itself.
Anyway, you now have a roll that’s tightly wound, experiencing hot and cold temperatures and is shrinking. all very slightly of course, but it now forms and holds this rolled-up shape.
In this instance, we are talking about a perforated vinyl which has about 50% less adhesion and hold on the lining paper.
Now, along you come and you lay it out on the table to trim it up, but the tight wound vinyl has still got the memory of that round core and as it rolls out flat. The paper isn’t affected but the vinyl is and wants to keep it’s rolled shape. so it starts to lift and create the tunnels across the width of the roll as the paper liner and vinyl start to separate. which in this case is easy because the perforated vinyl has only 50% adhesion on the lining paper.
this is very common with polyester and foil type vinyl like the cheap brands of chromes and prismatics. not for the shrinkage but more the forming of the rolled shape due to the time on the roll. if you are “cutting” it, it is even worse because the blade is trying to cut through the tunnels as it zips back and forth while the blades cutting. this normally snags or jams the cutter.