More than one same symbol timeout

I have to read multiple sheets with barcodes - mostly four different codes, some time three.

last of this four/three codes is smaller, so it is harder to scan it.

The problem is, that scanner read first code, second code, and first, and second and first and so on. same symbol timeout works, it never read the same symbol twice, but ... it still reads alternately first and second. How to fix it?