Buying stuff on Amazon US, zip +4 thingy problem.

I bought some hardwares from Amazon US this weekend, it will be sent to a freight forwarder then to where i live. But i think i might have run in some problems.

When i add the zip code for the first time, amazon add +4 at the end. (31666-2774), that’s alright. I got one order shipped to this address. But after that i had some problems and had to add my payment method and shipping address again, but this time amazon changed the last 4 numbers of the zip to (31666-3916). I tried to manually change it back to 2774 but amazon would automatically change it again to 3916.

All the rest of the address like street etc.. still the same, only the 4 numbers at the end of the zip changed.  

So, it’s possible that my packages will be sent to the wrong address?