Unwanted Non-knockout transparency group

[sd5e8a]

I exported a document from Indesign and then I decided to flatten some images in it, but for some reason I didn't want to go back to Indesign. Instead, I opened the document in Acrobat and I choosed Photoshop as an external editor.

The images are no longer transparent, but the Acrobat's Object Inspector still "sees" them as a Non-knockout transparency group (with its own color blending space and mode). I guess that this is a remnant of what was there before. So is there a way for me to get rid of this?

I tried that in Acrobat by going to its Flattener Preview and by setting the Transparency Blending Color Space to None for all the pages in the document, but it didn't work.

I'm also considering using 3rd party plugins, but I don't know how exactly to do it. There're several pages where this occurs.

Thank you

[sd5e8a]

I think that I found it: Acrobat > Print Production > Preflight > Select Single Fixups > Remove unecesary transparency groups. I clicked it and the unwanted group is no longer seen by the Object Inspector. But if I'm missing something, please tell me. Thanks.