In my earlier message in this thread, I noted that you should use Compute to create the ImplicitPlane. Is this the same issue that you bring up in the edit at the end of this last post? By using Compute, there is a memory of the original string used to create the object. If you use ImplicitPlane directly, then it immediately creates the ImplicitPlane's standard form and only holds on to that moving forward.
WeBWorK Problems
How can I get the answer entered by the student to be the one displayed?
This forum has a limit to the number of forum postings you can make in a given time period - this is currently set at 10 posting(s) in 1 day