No-index attachment URLS getting indexed

We have several attachment url’s getting indexed by Google.

So we used the Yoast plugin and enabled the option: Send attachment URLs to parent post URL. This is Working correctly.

After this Google was still indexing our attachment url’s.

So for the unlinked media attachment files we decided to no-index, follow them (with the Yoast SEO tool to).

But after we put this attachment url’s to no-index, follow, Google is still indexing new attachment pages every day now (with a no-index tag).

Like example: muurstickerstunter.nl/?attachment_id=95

What We should we do? Do we we need to redirect all unlinked media attachment to? I still find it strange google is indexing these attachment urls with a no-index tag.