Added an old-school GSC-10 to a bike while riding rollers indoors, worked fine, reporting speed as expected, indoors.
Took it off for an outdoor ride, forgot to disable the speed sensor, speed showed as 0 on the Edge 530.
Disabled the GSC-10 speed sensor mid ride, speed still 0.
Stopped/discarded ride, started new ride, speed still 0.
Power cycled Edge 530, speed still 0.
Removed sensor from settings altogether, now GPS speed shows up.
This isn't how it used to be, I don't think? GPS speed might not have priority over the GSC-10 when it is enabled, but once disabled, it should have.
Using v9.50 on the Edge 530.