When I read your post last night I think I let out a loud 'sigh' and mumbled to myself "Oh, dang it, I recall this one now. Another &*@# example of the current XenForo devs' not listening to their customers anymore."This problem came up on another Zenforo site. They narrowed it down to the 'Attach files' button at the bottom of the new-post window.
Thanks for reminding me; yes, the 'attach' behavior did change in XF 2.3 and some of us were pushing back on it when it was announced back in 2023. The "Cliff Notes" version is that they introduced a new change that tries to resize images on the client side instead of the server side and as part of that they strip out the EXIF from the original image, grab a small subset of it, and then add the subset of EXIF back into the smaller resized image on the client side before it gets uploaded to the server. For members it means likely faster upload speeds since some of the image processing is now done on their local machine instead of after it gets to the server but it completely messes with sites that are concerned about image quality and/or EXIF data.
On the other site, point their resident Code Monkey to this thread at XenForo and tell them to browse through from the beginning to see what's going on. For now the "Insert Image" option in the editor menu is still using the old upload method (as it is handled through the editor controls) while the "Attach" button at the bottom of the window is being handled with their new method. It it unknown what's going to happen when XF 2.4 introduces a new editor and in that thread I linked their resident Code Monkey will see that I'm trying to find a solution for the XF 2.3 "Attach" button so they'll want to check for any updates in that thread if they're going to implement something on their site also.
I really, really, really miss the old days when the XF devs' took feedback from their community into account for new changes. 🙁