Okay so I have some big in game errors all thanks to GOG, I've already submitted a complaint ticket and have gone more than 24 hours without a reply, it just seems like GOG doesn't give a shit about their clients and it's really making me upset there are a number of bugs that my witcher 3 has undergone since I updated and as much as I would like to fix it, the GOG client does not allow me to verify files.

If anybody can help me with 1 or all of these I would be so happy:

1. Rune Effects on Swords not working
2. Chamberlain glitches sometimes
3. Sound not working sometimes when I hit creatures
4. GOG client not verifying data any help would make me so grateful since GOG clearly doesn't care.

First and last game I buy using their software

Download the plain files, let them verify from the installer and do a fresh install. Only use the necessary minimum patches (i.e. not double-patching for interim versions).

I had some issues with the HoS DLC, but that seems to have been sorted with a reinstall and skipping an intermediate patch which was no longer needed.

Galaxy client can actually verify data, just click the game, click the 'More' button, Manage -> Verify/Repair

I Actually mean that GOG client is bugging and wont verify my game sorry for the misinformation This does seem to be my only option it's just a massive redownload, I guess I'll give it a try as soon as Blood and Wine releases.

GOG Galaxy is beta software so far. AFAIK it will not verify content, just "presence" of a file.

I had some problem with (carry weight) mod and I uninstalled it. Unfortunately some scripts were changed but "Verify/Repair" didn't find anything wrong. So I deleted that folder and GOG Galaxy downloaded (c.a. 30 MB of) files and everything runs fine:
https://www.gog.com/forum/the_witcher_3_wild_hunt/caranthirs_life_bar/post3