Alt key stuck after alt-tabbing to iTunes

I see that someone else asked this exact question a couple of years ago, but no replies. If I alt-tab to iTunes, it often acts like the Alt key is pressed, so if you type a song name, etc, iTunes performs various annoying actions instead of just accepting keys as text. Tapping the Alt key a couple of times toggles it back off. This has persisted for many, many years over several versions of Windows and iTunes. iTunes is the only app I've ever encountered with this problem, so I'd say it's something iTunes needs to address. Any ideas?