2000 Buick Regal signal lights

Front--back, both? Did you check bulbs--bulb sockets, where applicable, wiring connectors? At the rear, the turn and lower brake lites use the the same bulb filament, just, not at the same time. The problem is usually in the multifunction switch, but, if you want to check wiring circuits, we can do that. When the problem is ongoing, did you check applicable fuse/s, voltage on the fuse circuit?