The stainless steel protective film is bubbling. This happens occasionally, generally in the following situations:
1. The glue is not uniform when applying glue.
2. The temperature setting is unreasonable when passing the oven when applying glue.
3. There is a problem with the original film. Basically, there are occasionally bubbles when selling the film. Sometimes it is the quality of the manufacturer. If there are bubbles, the flat or stamping is easy to fly.