Can you help me understand why there is excess air in my frozen bag of vegetables?

 Based on the information you provided, there could be one of two possible situations.

1. Freezer burn – check the product’s best by date on the package. If the date has passed, time and temperature fluctuations may have taken a toll on the vegetables, i.e. degradation or freezer burn, resulting in excess air in the package.
2. Quality – If you have purchased the product in the past and the quality is off, I recommend you follow-up with the store where you purchased it or contact the food manufacturer.