URL param with substitution rule are not passed

If I call this directly URL

…/Exor-DE.nsf/Web-Page?ReadForm&wPageName=products&c=HMI%20Panels

params “wPageName” and “c” are visible in my agent, while with this substitution rule

/.html → Exor-DE.nsf/Web-Page?ReadForm&wPageName=**

if I call …/products.html&c=HMI%20Panels, that with applied rule should be …/Exor-DE.nsf/Web-Page?ReadForm&wPageName=products&c=HMI%20Panels

param “wPageName” is available and its value is correctly “products”, while param c is empty

Any suggestions or just a possible bug with rules?

Thanks