I would like to add that you can effectively use a vinyl letter removing solvent in case you want to remove the vinyl from your garment.
Heat transfer vinyl coming off.
You are trying to apply your decal to your favorite water bottle and after rubbing it down on your cup for 5 minutes the vinyl will not come off the transfer tape and release onto the cup.
Now you should have an idea how to handle heat transfer vinyl peeling off issue.
So all you need to do is increase the temperature 5 f to 10 f.
Some types of heat transfer vinyl are cold peel which means you must allow the vinyl to cool completely before removing the clear plastic sheet.
It is likely that your heat transfer vinyl is peeling off due to the temperature of your heat press.
These are the other possible causes as to why you will have a peeling problem.
Maybe you thought that it adhered properly but after a few washes you noticed the heat transfer vinyl peeling off.
For heat transfer vinyl to work correctly it must be melted into the fabric.