Can't move unless I hold down ALT

Hey guys, I am in need of some help. I have been trying to get my FiveM server to work, and I have succeeded somewhat.
The problem I am having is that whenever I try to join my server and spawn in, like 90% of the time my character won’t move at all (He can punch and look around just fine). I found out earlier today that if I hold down Left ALT while trying to walk around with WASD it works which obviously isn’t optimal.

I talked to one of the guys who helped code the server I downloaded and he told me it was a problem with FiveM’s newest update (If I understood correctly). He also told me that there was a fix for it, but for some wierd reason he didn’t want to tell me what the fix was.

The server is running on gamebuild 2189

Have any of you guys experienced this problem and found a fix? or do you have an idea of how I might be able to fix it.

Any help is much appreciated.
Thanks in advance.