The singer was the headlining performance Sunday night at the Carolina Country Music Fest in Myrtle Beach -- where she put on one helluva show that ended up getting highlighted by the fact there was a downpour that seemed to come out of nowhere toward the end.

As much of a spectacle as that was ... there was something else that caught fans' attention as Carrie was making her way offstage -- and that would be her going down, seemingly hard. Even crazier is the fact that it was caught on video ... and we got a hold of the footage.

Check it out ... it's a bit of a subtle moment, but if you look closely, you'll see Carrie take a bit of a tumble -- or at the very least, an awkward stumble -- as she starts to descend some stairs toward the back end of the stage.

In a flash, it almost looks like Carrie drops through a hole back there ... either way, her disappearance off the stage doesn't look all that natural -- and something clearly went wrong.

You can even hear people in the crowd scream out that she fell ... so folks certainly noticed.

Now, it appears Carrie addressed the fall -- she posted some photos from her gig this weekend ... and touched on something going awry at the end ... although it's a little cryptic.

She writes, "Well, last night sure was fun! And though the ending was quite unexpected, it made for a night we’ll never forget!" CU attached some emojis touching on rain and weather -- but it's possible she might be quietly referring to the fall at the end.