URI Rewrite not rewriting form action

We have a rewrite profile (of type URI Translation) that doesn't seem to be rewriting what we want it to.

I looked at the HTML that it should be rewriting, it seems to be called via a form action:

Could the hex encoding of the URI be causing it not to fire? It's looking for https://server1.contoso.com:8203/sap/ but it might only be seeing it with hex encoding of the special characters

https&x3a;&x2f;&x2f;server1.contoso.com&x3a;8203&x2f;sap&x2f;

Rewrite rules should work with form actions, correct?

I think I have the basics right, response settings has rewrite headers and rewrite content both checked, in the virtual server under Content Rewrite the rewrite profile is set, and the HTML profile is set to HTML - I don't know what else it could be.

We're on the following build: BIG-IP 11.6.0 Build 0.0.401 Final

Thanks!