The “Always On” category is a strange beast. In order for a device to be put in the always on category, it has to be on for a long time. Hence, when a device first turns on or off, it may take a couple days for “Always On” to change to a higher or lower value.
In the mean time, Sense tries to make sense of things by adjusting the “Other” category to try to make all the bubbles sum up to the total power drain reported by the CVTs. So lets say a device drawing 500 watts is lumped into the “always On” category suddenly turns off. The “always On” bubble wont be updated for a couple days so it stays at its old value but to make the bubbles sum up to the total power drain, “Other” is decreased by 500 watts. In a few days “Always On” will shrink by 500 watts and “Other” will go back to its usual value. But in the mean time “Other” will be much smaller and may even go to zero.
So I would chalk your experience up to Sense getting to learn your house and moving things into and out of the “Always On” category. Since it takes a day or so for the size of the “Always On” bubble to be changed, compared to the instantaneous change of the CVTs, “Other” has to shrink or grow to compensate for the time lag.