Signal level incorrect with mouse hover?

I'm trying to determine if my antennas will work as they are somewhat closely spaced. I'm following the full duplex isolation worksheet. In doing so, I've set my tune/rf power down to 1W, and am in CW mode, and using the 'tune' button.

I'm attempting to test ANT2 transmitting, with RX A receiving, first. I'll test the other combinations later.

I've got two panadapters open, with one slice each. One panadapter/slice with ANT1 as RX, ANT2 as TX. The other has RX A as RX and ANT1 as TX. I've got the first panadapter containing the active TX slice.

When I am on a blank frequency, I see -104dBm when I hover over the S-meter on the second pan/slice. When I hit tune (1W) the meter now reads -250dBm. However, on the scope, the peak goes up to 0dBm or so (hard to tell). I'm guessing this reading on mouse-over is incorrect? Am I doing something wrong? I engaged the RF attenuator and see the -8dB, and the mouse-over still eventually reads -250dBm. Interestingly, when I first mouse over, it starts higher, at -220dBm or so, and slowly creeps up to 250dBm.

I tested using ANT1 as the TX antenna, and the same behavior occurs. This time, the scope shows -40dBm or so, but if I hover over the S-meter, it transitions to -250dBm again, starting at -200 or so, then creeping downwards.

SSDR 2.1.3, Flex 6600M.