RE: Interesting problem ...input invited
Have other fliers experienced the same issue as you on the same frequency? Iwonder if a pager service in the area, is causing the problem since their operating freq's are not to far off the same range as the 72mHz bands. Also make sure your receiver is sufficiently protected from vibration. A good half inch of foam around the receiver and losely but securely fasten to the air frame is always in good practice. Iuse Velcro bands fastened to the airframe works great for me...
Keep us informed when you finally figure this out...