Hi, I've got a 4.1.14251417 install and I want to update to v4.1.1.4425968 and then on to 4.1.1.4494476.

However, when trying to install "Release - v4.1.1.4251417 Patch5_Hotfix4 + Japanese to Release - v4.1.1.4425968 - Patch Patch5_Hotfix5", I get an error "This patch does not support your version of the game please download a new installer". This is from previously verified files that are known-good for their version.

I suspect that the "+ Japanese" part in the patch name indicates the source of the issue.

GOG: can we please get the correct patch to bridge 4.1.14251417 to v4.1.1.4425968?

Does anyone have a source for the correct patch?

Larian never released that specific patch (+ Japanese) on GOG, it was an oversight & I'm sure Larian will correct it if somebody reports it.
I've reported it to Larian, though GOG make the offline installers, Larian must provide the files to GOG.

The current workarounds, are full reinstall of game, or let Galaxy do it for you
I just redownloaded the Full game, but I have 1 Gigabit Fibre, so it's just a 5 minute download for me.

The only other option is use Galaxy, as a workaround.

Note: even though I never use Galaxy to manage my games (I hate all Store Clients), I still now let Galaxy download huge offline installers, like BG3 with 30 *.bin files because Galaxy downloads them all with one click, usually they are all packed into a zip file, but this was first time I saw it just download the loose *.bin files, except for some reason it missed the last bin, (…-30.bin), so I grabbed that in my browser.

Really, GOG should allow the one click downloads on the website, I get why some users with poor internet may not want one huge file, but we should have both options.

it was not an oversight and the correct path is a full reinstall of the game

Larian does not even have post for v4.1.1.4425968 on their official forum because Hotfix#16 released as a total clusterfuck which they don't want to talk about

Gog makes the offline installs and Gog could have made an update path if they were willing to put the extra work into it but they when the 'full reinstall' path instead so your options are;
1 use Galaxy
2 full reinstall of offline game or
3 stop playing/ keep the older files