Almost every tube complaint is one of these two, and neither is really a materials problem.

Splitting at the shoulder

The shoulder is where the tube narrows to the neck, and it is the thinnest part of the wall. It splits when somebody squeezes hard.

They squeeze hard because the orifice is too narrow for the viscosity. Widen the orifice and the splitting stops, because nobody needs to force it.

Leaking at the tail

The tail is the flat crimp made after filling. If the seal width or the heat setting is wrong for the wall thickness, it holds on a shelf and weeps in a box.

Small sample tubes are the worst offenders, because the setting is often borrowed from a larger format without being re-specified.

What good practice looks like

Viscosity measured or a physical sample supplied. The formula run through the actual orifice before tooling. Seal width specified per format and checked on the line rather than assumed.

None of that is exotic. It is simply the difference between a supplier who asks about the product and one who asks only about the artwork.

What to check on a sample

Fill it, seal it, put it in a box and post it to yourself. Then squeeze it out completely and look at the shoulder.

Two days of that will tell you more than any specification sheet.