Template delegation (replacement) in Smarty 4

[lifecom]

My project uses CMS Livestreet (unfortunately not maintained).
This CMS uses Smarty v. 3.1.13 as follows:
1 -> 2 -> 3 -> 4.

Some plugins of this CMS delegate (replace) templates.
Template delegation goes like this:
1 (plugin class) -> 2 (extend smarty_internal_template) -> 3 (delegate function from plugin module)

After updating to Smarty v.4.4.1, template delegation does not work (templates are not replaced by templates from plugins).
What could be the reason and how can this be fixed?

[wisskid]

This is probably caused by an internal change in Smarty. I suspect in Smarty_Internal_Template. You could compare both Smarty versions and see what has changed.

[wisskid]

Closing this as this is probably not a Smarty bug.