Has anyone else been tested for gestational diabetes and had a partially positive 3hour test?

Possible. The 3 hr GTT is designed to diagnose diabetes. You need 2 out of 4 values above the following: fasting-95, 1hr-180, 2hr-155, 3hr-140. Only 1 abnl value is not diagnostic of gdm. Your doc may use a different scale or repeat this fasting test if you have risk factors. Some docs may start finger-stick checks 5x/day if you are "borderline" or just restrict your diet. Usually 1 abnl is neg for gdm.
I suppose you mean. A borderline positive test?. If indeed, yes it happens.