Bubbles are common in molded parts. However, they are usually inspected for this condition and easily corrected.
There's several causes. But most all relate to short cuts on the mold design or during the molding process itself.
In this instance, I'd guess it was more a function on the molding process. The bubbles are in the thickest cross section of the plastic. Usually a result of not "holding" the part long enough at pressure before completing the molding cycle.
This is common due to molders trying to maximize cycle time.
Shorten or eliminate the "pack or dwell" time to get more shots p/hour.
Clear parts are usually inspected closer exactly because the bubbles are so visible. There can be other contributing factors such as inadequate venting of the mold or drying of the plastic prior to molding.
Ya done good to catch this. I've rec'd mine but still waiting to install my new gadget. Like fishy, I waited patiently without complaint.
Watching the process is appreciated.
Excuse the hi-jack - now back to your regularly scheduled program.