Apple Mail Jenky Behaviour - Threading + Renaming Email Addresses

• I have used applemail for 20+ years

Today Applemail renamed every mail address in a group email - to the name of the folder I assign them to - overwriting the persons name. .. but it was not even as it is written my system; so I cannot even figure out the source of the re-write.

This year Applemail has started threading completely unrelated emails - sometimes they have a similar topic line, like 'website' but other times 'chat transcript' has been grouped with an email 'my photo and bio' - completely unrelated .. - this is nightmarish when building managing and multiple websites; clients email is tangled in with each other and the website provider - is there a way to manually unlink poorly linked threads/conversations without trying to unlink on the whole system?

I tried unlink conversations - this too is annoying to my workflow and in all folders the randomly linked conversations remain linked, anyway.

I looked at older posts about the threading /conversations - which seems to be a longterm issue, but was unable to find resolve to just manually over-ride .

• I have an M1 Macbook Pro, (tho its a little older and it is running Sequoia 15.6)
• I have apple intelligence and siri switched off, as I thought this may be causing the glitch