I received a very kind message from fidelio1976 with a solution:
Hi, I often saw this problem for other users and mostly it is caused by a windows login name with special characters like “ü,ö,ä,ß,é” or something like that (in Germany this isn’t unusual). Then the folder C:\Users\günter for example is a problem and a lot of failures could happen, because saving files in %localappdata% fails. Also some 3D objects in SIM are not shown or other planes can not initialize. I saw the WASM failure three times because of this. It is necessary to create a new Windows profile without special characters and reinstall Flight Simulator 2020
We have not have full verification yet by someone who reinstalled and can now fly H135 but this sounds correct to me, exactly this issue has been seen in similar fashion before in other products.
There is a work around with what @BlondeAcrobat62 wrote or you can change Windows 10 to use the new Beta UTF-8 language set.
To do that, you have to go to “Control Panel” → “Clock and Region” → “Region” → “Administrative” Tab → “Change system regional configuration…” → and check the “Beta version: Use UTF-8 for language compatibility” checkbox.
Thank you for the information, I just checked this box in the Regional settings of W10 and now the beautiful Airbus H135 bird is working perfectly …
I myself have in my W10 account name an accent on my first name “Gérard”, and with this single checkbox, I avoided the heavy task of creating a new account and reinstalling MSFS, an often hazardous operation. …
It is unfortunate that it is the users who solve the problems which I believe should be solved by Microsoft or / and Asobo.
Thank you to everyone who shared their experience so that people in difficulty can get their heads out of the water and fly with the machine they love.
Yes thank you very much, I saw this post and I already used to delete the community folder before each game start.
I can choose a registered flight without worry.
I do have erratic flight plans, but others are correct.
For the moment I will uncheck the “Beta version: Use UTF-8 for language compatibility” box when I fly in H135, then I will un-check it again if this flight plan problem is really recurring, and I will definitely do this. deactivation if I decide to leave the H135 on the ground for a while …
Published on 04/10/2021:
Finally, I wanted to test if the H135 worked after having unchecked the box mentioned above and restarted W10.
Well yes the beautiful bird works perfectly, and the flight plans which were corrupted are correct.
Also I had some incomplete added little scenes which are ok now.
Looks like the “WASM” has done its job with this box checked and even unchecked it still works.
Hope this can help someone …
In order to follow up on my topic, I just wanted to report some good news.
Indeed since the WU5 update I don’t need to do the manipulations described in the message, the H135 is operational without problems.
I don’t know which integrated function has been integrated in the WASM or because of an SDK update or another reason, but everything is ok now.