VM2 Search works in most cases but not always

[fmlk4u]

When I use a search function on website www.keyboard-centrum.nl and e.g. type CLP, it nicely gives all CLP pianos. However when I type "Tyros" or "Tyros-5" I get all keyboards as a result, instead of only the Tyros 4 and Tyros 4 versions/combinations as seen with link http://keyboard-centrum.nl/nl/winkel/manufacturer/yamaha/keyboards/orderDesc/by,product_price?language=nl-NL

Wierd effect is when I search for "Tyros 3" I get only product Tyros 3 which is expected. When searching Tyros 4, I get Tyros 3, Tyros 4 variations and Tyros accessories. But only Tyros gives all keyboards as output.

I tried to change the product name from "Tyros 5" to "Tyros-5" but that doesn't help either. Why does searching for "CLP" or "CVP" work greatly, but searching for "Ty", "Tyros", "Tyros-5" all give the same result of showing all keyboards. I hope I can soon get this fixed since december is coming.
Thanks for your help,

Regards, Fred

P.S. I use Joomla 2.5.16 with VM 2.0.20b