...Until a few days ago I was still activated by JSGME also packages #SAS and # TFM412. Is it possible the classfiles comes from these packs...
No Marco, irrelevant, they use different mod folders. The JSGME options that come with the CUP Downloads are perfectly safe. Mods from outside of that environment are your own business. I'm just advising caution and pointing out, in advance, the bad ones that I know about. Also earlier mods that change the CUP ini-files are going to break it.
Part-18 + Part-18B + Fixes is a CLEAN START.

Mc-202XIICB problem SOLVED! Missing SFS in my setup.
Thank a lot Simon for your assistance.
Alex
EXCELLENT! - this is from page-8 of the new CUP Manual...
4) There are only three possible reasons for ANY failure.
4a) Incomplete download or wrong placement of SFS content.
4b) Incomplete download or wrong placement of Mod Folder.
4c) User altered Mod Folder or SFS Content.
In this case we hit the answer for you with the first shot, 4a,
Incomplete SFS...
1) when I try in QMB to open the PBY Nomad I get directly a CTD...
2) I installed the first WOW adder...got a CTD between 60 and 70%...
Best regards.
Answers and fixes:1) This didn't all happen with Part-18. However, the new classfile structure is very disciplined and removes all conflicts, duplicates and redundancies. Obviously we have been a little over-zealous in places but it is easily fixed.
I would urge enthusiasts to read the manual too, especially the 8-Page section on 'Understanding CUP'. It highlights the robustness of the modular setup and the fact that SFS encoded data is better than loose mod folders and a chaotic approach.
For example; nothing about the PBN could be damaged as it is safely nestled in SFS format. Obviously I hoovered up too many loose classfiles. In less time than it took to type this I found them and put them back.
Therefore, here is the fix: All accumulated fixes of this nature will seamlessly become Part-19 in time...
PBN FIX;Missing classfiles for PBN Nomad. UnZIP/UnRAR Straight to your main Il2 directory and allow overwrite.
https://www.mediafire.com/?fi5x10o7a6xetx82) Read also about Restore Point installs and do not add OLDER mods that alter the CRITICAL *.ini content of CUP and expect it to work.
I appreciate the heads up on the Nomad, tartenmuche, thank you - Remember that Part-18 + Part-18B + Fixes is COMPLETE and not backwards compatible with anything older. Restore Point install means: We start again from here, looking only forward...

Homing X-4's......my god don't let that loose on Multiplayer!
OK, all good then? Classfiles again - My bad! They are locked into the new structure now and backed up. Don't mess with it people!

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THE NEW C.U.P. MANUAL V6.0https://www.sas1946.com/main/index.php/topic,49964.0.html*************************