Bill,

In all likelyhood the problem is not with your UAT but with your fuel system picking up air somewhere upstream of the UAT. The UAT is doing its job by preventing that air from getting to your turbine and causing a flameout. However, that much air in 5 minutes indicates a leak somewhere.

Check all your fittings upstream of the UAT. Safety wire where the tubing goes over fittings and avoid Festo fittings. Fuel caps are often a source of leaks so check they are tight, seal them with silicone if in doubt. It's also possible you have a hole in a pickup line inside a fuel tank which can be difficult to detect.

As for the UAT itself, make sure the cap is very tight and the knurlled fitting in the center of the cap is tight as well. The intake and fill lines connecting to the UAT should also be safety wired and make sure your fill line plug is air tight.

And yes, keep fuel in your UAT at all times. This helps keep the filter bag saturated and free of air.

Keep your flights short and keep looking until you fix the problem!

Craig