Search / Order / Missing Product

Hi Community,

i have a strange behaviour with my search.

The Problem is that searching for a product like "fpo20" i do not find all Products with "fpo20" for example the "FPO2091" is missing.

http://agristar.pl/index.php?route=prod ... &limit=100

BUT

if i change the sort order to DESCENDING for example choosing NAME Z-A i found all products, so that the "FPO2091" is not missing anymore.

http://agristar.pl/index.php?route=prod ... &limit=100

Why is this happening? I am really crazy about this.
Any help appreciated!

I am using:
OC 1.5.4
AND this Extension
http://www.opencart.com/index.php?route ... ASC&page=4

No one can help?

I HAVE THIS EXACTLY SAME PROBLEM.

HOW YOU FIX IT?

THANKS!!!!