Issue with hidden fields at registration and then becoming required after error

I've got 4 registration forms with different fields across different tabs for different sub levels. These fields are hidden in the plan settings and are not normally visible and the registration mostly proceeds as normal. The unrequired tabs are hidden by css.

However, when there is an error (user hasn't completed a field correctly or missed a required field) it then reloads and shows the hidden tabs and hidden fields which obviously makes proceeding impossible.

This appears at the /saveregisters part of the reg process.

The question is : how can I prevent these hidden fields and tabs from ever showing when not required?

Sounds like the plan selection javascript isn't triggering on re-display when there's a server side validation error blocking the registration. Does re-selecting the plan clear up the issue? That'll at least let us know that the javascript at least still works.

Retested the following scenario.

Plan A hides Field A
Field B validation requires a value higher than 100

First selected Plan A and confirmed Field B was hidden. Input a value of 5 for Field B then attempted to register. Registration failed with validation error where Plan A was still selected and Field A was still hidden. I repeated this test twice using exclusive and non-exclusive plan.

Seams like it's possible something maybe interfering with this behavior on your site

Not sure what you mean but refreshing the page and reloading the form content still shows the issue. I've tried it with and without SEF urls - no difference. There's nothing in the console error panel either.

How would I determine that the plan selection javascript is working or not?

Unselect and re-select the plan or is there only 1 plan available preventing you from selecting it to begin with?

There isn't a way to select/unselect a plan. The plans are added to the (hidden) CBSUBS plans menu and then those SEF urls are linked from the membership intro page.