I have installed a game via the backup installers and since then also patched it with the same installers. The last patch went wrong saying 'some errors occured' and giving a patch log saying 'Error modifying file'.

I then have launched in GG the 'Verify / Repair', and when launching the game I see by the version number that the latest version is installed.
Will Verify / Repair always update the game to the latest version, or is my patch incomplete because of the error above, so that I must re-run the latest patch?

Thank you,

it checks your install folder against the backup copy Gog has then downloads any missing or changed files... you used the backup installers? you mean the off line installs because Verify / Repair is a option with Galaxy and the off line files may not be as up to date as the files stored in Galaxy

its a game by game senario mate... some take months to catch up and other come out more or less at the same day as their Galaxy update

also 3rd party software like Microsoft runtimes are not normally part of a verify so some games 'BG3' for example may still need to actually be installed before they will play for the 1st time on some systems