One dim parking light?

Or one bulb was reversed.

1157's are dual filament bulbs and must be installed with the correct orientation in the sockets, but can be forced in 180 degrees out if you do not pay attention. If one is backwards then its brighter blinker filament will be connected as the parking light on that side and the parking lamp intensities will be mismatched.

Note that the bayonet pins on either side of the bulb base are at different distances from the base; the sockets will have the same different locations for the bayonet pins so you should not be able to reverse the bulbs. But, sometimes the sockets get spread a bit an it is harder to tell if you have them inserted the right way, or backwards.

Try the blinkers as well as the parking lights. If both parking lights are the same intensity, and both blinkers are the same brigthness (and are noticably brighter than the parking lights), then you have both bulbs in the sockets correctly.