Diagnosis
This is normal, especially with a new system or after a filter change. It's dissolved oxygen coming out of solution, not a contaminant. The water is under high pressure in the membrane and tank.
How to Fix It
Let the water sit in a clear glass for 30-60 seconds. The bubbles will rise and disappear from the bottom up. This is a visual issue only. The water is safe.
If That Didn't Work
If it's persistent and tastes odd, you may have a leak on the suction side letting air in. Check the pre-filter housings (stages 1 & 2). Ensure the O-rings are lubricated with silicone grease and the housings are tightened securely by hand, not with a wrench.
Heads Up
Cloudy from bubbles is fine. Milky white that doesn't clear is a problem. If it doesn't clear, the membrane may be compromised or there's an installation error allowing unfiltered water to bypass.