2008 Kia Rondo #5 misfire

The Check Engine light flashes when too much raw fuel is going into the exhaust system. That will overheat and damage the catalytic converter. In the absence of any other fault codes, that usually means there's a spark-related problem because a grounded injector control wire or a shorted injector driver circuit in the computer would be detected and set the appropriate code. Since you don't have that, spark, compression, and valve timing aren't monitored and can't set any codes, and timing can't be off for just one cylinder, and loss of compression wouldn't send unburned fuel into the exhaust system.

You didn't mention the spark plug. That would be much more likely than an injector or ignition coil.