Text Messages Date/Time Same, All Set To Phone Turn-On Time

Same question as this: (over 300 people report to have the same issue)

https://discussions.apple.com/thread/250247544

Every time my phone updates or restarts, all the texts messages are changed to the same date and time.

This is very inconvenient and makes finding recent messages from hundreds of threads very slow and cumbersome, certainly not something that iPhone users expect (compared to Android).

I think this started happening when I ported from Android to iPhone a few years back, so I'm guessing there is some corruption in the messages database, or the original dates missing or wrong format. There must be a way of resolving this (don't say 'delete all messages', that's not a solution. Like 'reinstall Windows'.)

Any help or pointers to utilities that can deal with this are appreciated. Thank you in advance.