1Password's use of Secure Input

I just permanently lost actual note data because of this.

I was editing an item in the main 1Password window, so I had text selected.
I clicked to open Calculator.app from the Dock. It appeared on screen.
The keyboard focus unexpectedly stayed in 1Password.
I began typing my arithmetic sums.
This overwrote the text selection in 1Password.
I had to switch to Calculator.app a second time to make it active.

Focus theft occurs on the Master Password screen too.

Quit 1Password completely
Open 1Password to the Master Password entry screen
Click to open another app from the Dock
Wait for the app to open
Hit Command-Q to quit the other app.
1Password quits instead.