Name images changed after installing plugin

Hello people!

Hopefully you can help me. I have a website where the images are nicely indexed and we are easy to find. Now something, after installing this plugin, changed, so I got the message from google webmaster tool that many more 404 errors (about 1700 in the last couple of days) have occurred. After some hours of searching, I see that it is the name of my images.
For example, this was first the name of an image:
https://www.vintagevirus.nl/tekoop/vintage-industriele-kruk-atelierkruk-met-mooi-onderstel-gemaakt-in-de-jaren-70/img_4625/
So now I get a 404 report on this result. This is the name of the same image now:
//www.vintagevirus.nl/?attachment_id=6272
And every new image I upload also gets this name instead of the SEO friendly name I used to get.

I would very much like to have my first name back without a 404 report. Does anyone now what can have happened?

Now I know how to adjust individual images, but since we have about 10,000 images, that is an impossible job. Thanks for the effort!!

Best regards. Hanneke

[ Please do not bump. ]

The page I need help with: [log in to see the link]