The Callsigns of these ghost flights are:
FLG3634, ASQ4900, DAL845, DAL1295, DAL1725, DAL1580, DAL2199, DAL755, DAL2349, DAL2496, RPA4928
Altitude of these flights are around 1000 feet, located near middle of Taiwan, passed through mid-Taiwan from east to west.
With that altitude 1000 feet, they will hit the mountain. Hence I think those were ghost planes.