The answer to 'why is my roof vent sagging' is that it is likely due to improper installation, aging materials, or structural issues with the roof. Roof vents can sag over time due to the weight of the vent and the elements wearing down the mounting hardware or roof deck. Symptoms of a sagging roof vent include a crooked or uneven appearance, gaps between the vent and roof, and potential leaks around the vent.
To fix a sagging roof vent, you may need to re-secure the vent to the roof, replace damaged mounting hardware, or even replace the entire vent if the roof deck is compromised. While minor adjustments may be possible as a DIY project, significant repairs or replacement of a roof vent is best left to a professional roofing contractor to ensure proper installation and avoid further damage.