Whether or not you are trained, listen on the .03 repeater any time there are weather warnings posted for the immediate area. We're all amateurs. Hiram lived in the Hannibal area and was a long time employee of Gates-Harris, retiring about 20 years ago. Our condolences to his family and many friends. It could be directivity.
Directivity is never perfect.
The forward sample always contains some reflected power, and the reflected signal always contains some forward power. The error usually will be small since the forward signal is much larger than the reflected signal and only a small percentage of the reflected signal will be picked up. This is because reflected signals usually are so low in level that even a small percentage of the larger forward signal becomes quite significant. To test directivity, the coupler is operated with forward orientation into a reference terminator with a return loss which exceeds expected directivity and a forward reference level is measured. The impact of directivity on VSWR measurement accuracy is most easily calculated by working in reflection coefficients.