I have the same problem. It doesn't mader if this mod is below or above the swap body mod, it always crashes when you select a rigid chassis from Kast.
The only error in the log is that (00:02:06.948 : <ERROR> Cabin accessory is missing!),
But it doesn't crash when you select Glovers MAN TGX E6 or the SCS DAF 2021. There both mods can coexist and have no bugs.
Wish i could run both mods on the new MAN.