Oh well, the AirGroup problem again ...
Please apologise, I forgot to omit these entries from the *.cfg files.
The CTD occurs when no airplane named LBSWalrus is installed.
I replaced the download archives; the *.cfg files have the ArirGroup entries now removed.
P.S.: Folks, consider to find you the Walrus converted from SH5 to SH3 by Textpilot's. It's nice, even that the texture is very bleached.