Thank you for your response. I have now reached out to PuTTY and their reply is similar. I will look for other causes.

We are not authors of Pageant, you better ask at PuTTY site.

Anyway, I do not think that Pageant ever removes the keys on its own.

Using the native task scheduler in Windows 10, I am loading two private pageant keys whenever I log into my computer. They are password protected so I am prompted to enter a password. The computer runs 24 hours per day and I only shut it down to perform maintenance and updates. I have automated routines that use WinSCP scripting to pass information to and from several different sFTP servers. All appears fine and everything works for a few days.

However, every few days, one or the other key unloads itself and my automation routines abort. What may be causing only one or the other Pageant private key to disappear by itself? Things have worked fine for the past 10 years without this happening. It only started within the past two weeks since I started loading two keys instead of just one. The password for both keys is the same so I am only prompted once; however, I can confirm that both keys are initially loaded and the systems are working for a few days as expected.

Thank you, in advance, for your assistance.
--Dean