Magento 2 - How to override knockoutjs template which is already overriden from a third party module?

Question

I try to override the knockoutjs template vendor\amasty\module-single-step-checkout\view\frontend\web\template\checkout\summary\item\details.html from my own Theme.

The module amasty\module-single-step-checkout is registered as Amasty_Checkout

Attempt:

I copied the file into my theme at THEME\Amasty_Checkout\web\template\checkout\summary\item\details.html and made my changes, then I flushed the cache and the browser cache, but it still loads the old template.

I also executed grunt clean to clear static files. But it does not help either.