According to RFC 3986 the query string must come before the named anchor (fragment).
I have a couple forms on a page on my site where you can use a named anchor, and then query string parameter, and it works OK:
[SITE REMOVED]/?enquiryType=Resellers#testing
Try without the enquiryType to see the drop down with no selection made, and then try with it to see the choice selected. You can try without the named anchor as well.