Rectangle Blue Outline On My Canvas

[Chris Panny]

Newest PS | Big Sur 11.2

I have a PS document that I created with a 2500 x 2700 artboard. After shuffling some of the layers around and doing some minor edits, I suddenly noticed this rectangular blue line on the canvas. I can't select it with the Move tool, Path Selection, Direct Selection, can't hide it (CMD+H or CMD +;). I jumped back history states, but it's still there. I deleted the artboard, leaving just the layers and it's still there. I turned off all of my layers - still there. 

I did just discover that when I resized the widths of two vector rectangles, both selected and equal in width, via the Properties panel, I saw the blue outline.

What is this thing and how do I get rid of it?

[c.pfaffenbichler]

Could you please post a screenshot taken at View > 100% with the pertinent Panels (Toolbar, Layers [with the selected Layer visible], Channels, Options Bar, …) visible? 

What happes if you deselect all Layers? 

[Chris Panny]

Attached is another shot at 100%. It was too big to get it all in at this zoom, but it shows the top vector shape. I turned off all of the other layers (linked images, text). Because I was under a time constraint, I had to make a new document with the same settings and just copy everything over from the old one. In the process, I overwrote the old file with the blue outline and now I'm unable to recreate the issue. At least you can see the panels.

[c.pfaffenbichler]

It seems to me that may just have been the preview of the Path when the Shape Layer is selected. 

[Leslie Moak Murray]

Try View>Show> And uncheck "Guides"  - they might be just the blue guide lines

[Chris Panny]

I tried that. I didn't make any guides for this project.

[Leslie Moak Murray]

View>Show>Layer Edges, and uncheck it?