I've set up a Service Item, with some custom Resource fields.  There are also some Field and Form Rules.

Thanks to these rules, when I access the form (as a requester) using Google Chrome and change the contents of the "Item required" field, the Category, Subcategory and Item fields change as a result:

However, when I access the same form via Internet Explorer (11.0.9) this does not work. 

Full rule:

It sits amongst many other rules:

Is this a problem in the way I've implemented the Rule, or is this a known bug in this version of IE?  Does anyone else have this problem in a later version?