First you need to check and make sure that you have good grounds.
Both flashing usually indicates that power is backfeeding, often from poor grounds.
Then pull the bulbs out and check for power at each light socket. If you have power at both sockets, using a good ground for your test light, then you have a short in the wiring.
If you don't have power to both light sockets with the bulbs out, then you have a ground or bulb problem.
Have you replaced the bulbs with "KNOWN" good bulbs that are the correct ones for your vehicle? If not, how do you know the bulbs are good?