Multiple prompts for "New server fingerprint"

I'm connecting to Ultraseedbox using SFTP.

Since yesterday, I keep getting a prompt saying that my server fingerprint has changed. I click "Add" but the prompt keeps reappearing. Ultraseedbox say the fingerprint hasn't changed since June 2020, when they last performed a server reinstall.

Any ideas what could be causing this and why both Update and Add options only dismiss the warning for a few minutes before it reappears?

Please attach a full session log file showing the problem (using the latest version of WinSCP). No need to hide a fingerprint of host public key. It's a public information.

I exported my WinSCP settings before removing my other servers so that my logs wouldn't include unrelated servers. When I inspected the config export .ini file, I noticed two old SFTP accounts I used to have with UltraSeedbox were still cached somewhere, even though it was not obvious in the GUI.

After deleting all instances of the old/invalid SFTP accounts and two outdated server fingerprints from my backup file, I re-imported the config backup into WinSCP to purge those settings and retested an upload to UltraSeedbox.

So far, everything seems to be working perfectly!

If the problem returns, I'll upload a log file.

Thanks for your feedback. Let me know if you are ever able to reproduce the problem, as this should not be happening.