The Princess of Wales has already copped to altering the picture seen round-the-world -- but neither she nor Kensington Palace have clarified what exactly was doctored and how. According to Sky News ... metadata for the original photo -- which they seem to have obtained -- shows the picture was taken at their Adelaide Cottage home in Windsor.

They also report that the metadata shows it was taken with a DSLR camera ... and more importantly, it was apparently saved twice in Photoshop on an Apple MacBook -- once on Friday night and again on Saturday morning before it was released to the public by the Palace.

Remember, when it first went up on social media -- Prince William was credited as the photog -- and they said this snap was taken last week sometime ahead of Mother's Day.

Now, though, in light of the photo being reported to be manipulated -- and Kate falling on the sword as the one to blame -- everyone is picking this photo apart and analyzing it to see exactly how it may have been tweaked ... and we actually have some ideas of our own.

Take a look at what graphic designers in our own building say are apparent Photoshop edits ... or more accurately, Photoshop fails. The big red flag everyone has been pointing out is Princess Charlotte's hand overlapping with Kate's left hand ... where you see a blur.

Our own experts say this seems to be a bad use of the stamp tool in Photoshop ... that, or a possible flub in duplicating layers of two different images and not lining them up correctly.

In terms of Kate missing her wedding ring -- we know magazines are notorious for editing stuff like that, including copying/pasting body parts ... and our team here says that may well have been what happened with Kate's hand here. Basically, that whole section looks edited.

There's also the issue of Prince Louie's sweater pattern not lining up -- something our team noticed -- and Kate's jacket zipper seemingly disappearing and reappearing in the shot.

Even Kate and Charlotte's awkwardly overlapping appears to be a Photoshop mistake ... that's our own team's take anyway. It's just a handful of apparent mistakes we honed in on -- but there are certainly more others have picked up on ... and the conspiracies are flying.

Some are suggesting that Kate's face here is actually cropped from a Vogue cover -- but according to our graphic designers ... that doesn't seem likely since the lighting is all off.

The Palace isn't explaining itself here ... at least not fully. We've reached out to them for further explanation on what exactly was changed here -- but haven't heard back yet.

There's more intrigue ... with a new photo of Kate riding with Prince William as they drove to a private appointment -- and here, too, she's heavily obscured ... shying away from cameras.

It's the latest shot paps have gotten of her outside of Windsor ... but it's hard to really see her.

At this point ... people are calling for Kate to just come out and address the public -- because anything short of that won't appease everyone's curiosity or suspicions. With the fake photo being put out ... it's quite clear that Kensington Palace was okay with trying to pull a fast one -- or at the very least, wanted to make her seem like she's doing better than she is.

One last thing ... a lot of people have suggested AI is afoot in this Mother's Day pic -- but we talked to AI expert Paul Dawes -- CEO of More.Ai -- and he tells TMZ ... this photo appears to be more Photoshopped than AI-generated ... although it's possible it could be.

Dawes says an AI tool may have been used to edit real photos -- but this image does appear to be thrown together with actual photographs of real people ... that's his take.

Ditto for AI expert Mike Gioia of Pickaxe, who says this picture is likely more Photoshopped than tinkered with AI. He tells us the teeth, hands and eyes all seem fairly normal (or human) ... and he would know, as those are telltale signs of whether AI created it, or if it's the real McCoy. In this case, he says he thinks these features look more authentic than not.

Gioia does say this might've been created with the help of something in Photoshop these days called Generative Fill ... which uses AI to pop in generic images. It's just hard to tell.

Bottom line ... this is a bad Photoshop job -- but the question remains ... WHY??? Kensington Palace has been tight-lipped ... and they're letting Kate herself take the heat.