"Files might be harmful" warning btw 2 drives on same PC

I've got a weird situation here. I'm copying some files from my main data drive (D) to a second hard drive (E), and every time I try to copy I get the "These files may be harmful to your computer" popup warning.

It's odd enough that the "harmful" files have been on my D drive for years (if they were harmful they'd have caused harm long ago) but the message only appears when I'm using two windows of File Explorer. If I copy the files within the same window, no warning.

It would be simple enough to use just one window, but since File Explorer insists on expanding the file tree to the left, I have to keep scrolling up and down for each file copy. To cut out that nonsense, I use two windows side by side.

I've done this many times in the past without issue; the warning is new as of today.

Both drives scan clean for errors and viruses/malware. I bought both new, and have used both before. In fact, the E drive used to be my D drive (I upgraded for more space on D). And to repeat, this only happens when copying with two File Explorer windows, not within a single window.

I know the procedure for allowing files between networked computers, but I can't figure how to make this work on the same computer.

Any help you can provide would be appreciated.

As a file manager, Explorer is the worst.
Try Freecommander