I don't see any issues in the code. And you have an event that destroys the bullet if its speed >400, so bullets can not travel faster.
Try running the project in debug mode, when second bullet is spawned, pause the game and compare both bullet instances - check that they are on the same layer, compare their speed etc. Maybe you'll find the problem.
If this doesn't help, please share your project file. You can remove everything non-essential from it.