Issue With Clean_Price

I'm having an issue using clean_price on some of my tpl files, where clean_price all of a sudden seems empty.

I made some changes in the past to the files:

In each file the clean_price variable is assigned:
{assign var="clean_price" value="clean_price_`$obj_id`"}
At the right place I then used to display the variable with number_format
This always worked, but when I found out that the price didn't update when picking some options, I tried to make some changes to templates\blocks\product_templates\default_template.tpl to see if I could fix the issue.
But strangely enough it now seems clean_price is empty, but not only on default_template.tpl, but also on all the other templates even though I didn't change those files.
The thing I'm trying to display is an ex vat price, but this price also needs to update when choosing options.
I found this topic:

And tried to add:
{$smarty.capture.$price nofilter}

This works in the way that it gets updated when choosing an option, but it's not the right value.
I tried to replace {$smarty.capture.$price nofilter} with {$smarty.capture.$clean_price nofilter}, but again, it appears to be empty.

P.S. Yes I did ?cc&ctpl to clear cache and template cache

Make sure that your VAT is not set to zero.

Sorry for the delay, been a bit busy.

As I said in my post, it always worked fine on normal products, it just didn't work correctly on products with options when changing those options.
It's not new products I'm talking about, it's the same products that always showed clean_price just fine.

It's just that for some strange reason clean_price is now returning an empty value.