using iRule to replace uri not working as hoped

I am submitting this on behalf of customer. He wrote this irule, it seems to be changing the uri as needed, however the client browser is sending rst and killing session. Are we doing anything wrong here?

When customer points browser at http://x.domain.com/URI1 without this iRule in place, his page loads just fine. When we goto http://x.domain.com/URI2, the uri gets changed to URI1, however the page does not load.

There is only one member in the pool. Is there anything you can think of that would be wrong? Thank you.

rule uriMod {
  when HTTP_REQUEST {
    if {[HTTP::uri] eq "/URI2"} {
      HTTP::uri "/URI1" 
      pool httpPool
    }
    if {[HTTP::uri] eq "/otheruri"} {
      HTTP::uri "/" 
      use pool http2pool
    }
    if {[HTTP::uri] eq "/thirduri"} {
      HTTP::uri "/xyz" 
      pool xyzpool
    }
  }
}