Microbubbles are clusters of bubbles showing weeks or months after especially on flat areas.
Although microbubbles show up in the flat areas where there is no stretch nor heat involved, this is caused by the lack of squeegee pressure during application or missed spots. This issue is also prevalent in colder areas or when the season turns to winter because the surface temperature is too low during application.
The graphic looks smooth and fine until you put some heat to it because heat will reveal any air underneath the film because it will expand.
Microbubbles is also a sign that the wrap wasn’t post heated properly or pressure wasn’t re-applied.