The global and local states match on the master machine.
On the slave machine, the global state is reported as 1 file more (literally 1 file) than the master global state, and the local state is reported as 1 more file still (a total of 2 more files to the master global state)
There isn’t a mismatch between shared folders otherwise.
However you are right that the slave machine was reporting “Failed items” a few days ago. This has now rectified though, and on the left-side of the UI on both machines, it says up to date.
My best theory right now came to me a few minutes ago after having read through all of this thread HELP: Syncthing is redownloading already existing files! - although the topic was about re-downloading existing files (which has happened to me before and I could only solve it by deleting the file altogether) the topic was fascinating to follow and I see that you eventually found a solution in telling the user to delete the metadata blocks and let it rebuild. What was also very interesting though is that the corruption came about because of the “variable sized blocks” feature. In my case, I have been ticking that box at different times recently for different folders on each machine, so I am now suspecting that doing so has lead to Machine A reporting the Machine B state incorrectly, because of the way things have been hashed.
I am thinking of turning off the variable blocks on the shared folder on both sides, and letting it re-scan/re-hash - do you think this would be worth trying? Might be faster than deleting the index altogether. This is my best idea right now other than deleting the index, which would affect all the other shared folders!
I also concur with the user on the other thread - despite these issues sometimes, Syncthing is a brilliant piece of software and I’m very grateful for it. Thanks for all the amazing work to all the team.
(One aside question - as a rule, with a mixed folder of many small files but also many large ones, i.e. thousands of photos with dozens of large ISO files, is it better to have variable size blocks turned on?)