I have seen mine do that a couple times.
The voltage will be going 7.21 - 7.20 - 7.19, then for some reason it will go 7.28, then right back to 7.18, 7.17, etc
I assume it is some glitch in the T35 - Doesn't do it everytime, but now and again it seems. Maybe mine needs a tune-up....lol..