My process that resulted in the below screenshot, using speedy entry with an attached MIDI piano: 

1. Hold down C on my piano, press the 5 key twice. 
2. Press Alt + Tab to pull up my reference sheet music in another window.
3. Press Alt + Tab to pull up Finale again. 
4. Hold down just the A key on my piano, press the 5 key twice.

It seems to be maintaining the C value even when the piano C key is not being held down. I often use reference sheet music in other windows, and placing them in side by side windows doesn't leave a big enough display area for feasible use. I can alleviate it by clicking outside of the measure, but that requires moving my hands off the keyboard every couple notes, which adds a ton of time to the otherwise streamlined process.

This happens every time I switch windows, but it only started today, this hasn't been an issue before. I restarted Finale, my computer, unplugged and replugged my piano, and there are no available updates. Windows 11, Finale version 27.3.0.137.