Spot healing gives me "not enough pixels" error

[Joshfree]

I am trying to retouch a photo using the normal Spot Healing brush. No matter what I do, I get the "not enough pixels" error. The files seems to be 100% normal. RGB mode (tried CMYK as well). 8-bit. (Tried 16-bit.) It's 100% opaque except for a normal mask. It's one layer. It's not locked. Things I have tried so far:

• Resetting preferences
• Testing another image (it works fine)
• Saving the image as a TIFF, a PNG and a JPEG (the JPEG works; the TIFF and PNG don't)
• Pasting the image from one file to another.

Because the JPEG works, I assume this has something to do with transparency. But I have never seen this behavior before, and I've used Photoshop for decades. I have the current Creative Cloud version.

Does anyone know what's happening here?

[c.pfaffenbichler]

Could you please post screenshots with the pertinent Panels (Toolbar, Layers, Channels, Options Bar, …) visible? 

[Joshfree]

Thanks for the response.

I saved the file as a PNG and worked on it from there. Obviously had to collapse all the layers, etc but at least it worked. Have not had time to recreate the problem since I posted. If anyone is sincerely interested, I'll try to do that.  Otherwise, I'll see if it ever happens again.

[c.pfaffenbichler]

If it does please post the requested screenshots to clarify the actual situation (Layer-wise etc.).