A slice has an rxant and a txant, and each pair belongs to that slice's
own band. Only two of the four were being set — the downlink's receive
antenna and the uplink's transmit one — so the downlink slice was left
with an empty txant. It never keys, so nothing was wrong on the air, but
the slice was half-configured: move transmit focus to it and the radio
uses whatever antenna it happened to be left on. Reported with XVTA on
2 m and XVTB on 70 cm, where the 70 cm slice showed one antenna and the
2 m slice showed two.
SatAntennas now takes all four, and the late-slice replay in
adoptSatSlice hands the uplink its own pair instead of putting the
transmit antenna on both of its ports.