If something spontaneously changed, we'd not know why unless we can see the transmitter. Even so, it may operate normally. It is possible that there's a bad memory chip inside the unit, but is acting intermittently. It's also possible that the programming was accidentally disturbed, and nothing's wrong.

A 10.8V reading is normal. The transmitter would be considered nearly discharged when it gets down to about 9.4V or lower.