[valych]

It is happening because when player presses multiple keys, variable oldkeys is different from KEY_FIRE. You shouldn't check key pressing in the way you did.

PHP код:

if(oldkeys & KEY_FIRE) 
{
    // Your code here
} 


For more detailed information see the wiki page (https://sampwiki.blast.hk/wiki/OnPlayerKeyStateChange). You will find a lot of useful advice and functions to check keys pressing.

About "How to check for multiple keys" (from the wiki page):

PHP код:

if ((newkeys & KEY_FIRE) && (newkeys & KEY_CROUCH))
{
    //.....
}