My EagleFiler icon seems to have a blue blob in it both in the dock and in the command-tab switcher. If I “Get Info” in the finder, the icon is right.
I’ve tried replacing the icon with the icon from a fresh download, it doesn’t seem to fix the issue.
Which version of macOS are you using? What kind of Mac? Does it still occur if you reboot your Mac in safe mode?
My guess is that this is caused by a macOS bug, as I’ve seen similar graphics glitches recently in a variety of apps when viewing image files or PDFs.
FYI –
Yes, perhaps something awry in MacOS Big Sur handling of app icons in Dock and Switcher?
I have an issue with the Fantastical icon showing as the (Apple) Calendar icon in the switcher, and occasionally the same in the Dock – but not always.