Deleted message threads keep reappearing both on my MacBook and my iPhone
Texts that I deleted up to a week ago keep reappearing, both on my iPhone and my MacBook (but at different times for each). On the MacBook, I deleted again, logged out of iCloud, then verified that they were not showing on my phone before logging back in. And still they came back a couple hours later. All of these messages are SMS messages (i.e. not iMessages) -- but I don't delete too many iMessage threads, so that may not mean anything. When they come back, they show as Read. It's not as big a deal on the iPhone as it's relatively easy to delete many message threads, while on the MacBook each message must be deleted separately with three mouse clicks/keystrokes per message.
macOS Big Sur running on mid-2014 MacBook Pro,
iOS 14.6 running on an iPhone 12.
MacBook Pro Retina