I've been using Thor 1.5.14 for about a month. It's been great so far.
Sparkle automatically detected the new 1.5.16 update. After it downloads the new build, it reports:
"Update Error!"
"The update is improperly signed and could not be validated. Please try again later or contact the app developer."
This is happening on two different Macs, both running Sonoma 14.7.