There is a serious issue regarding SSD analyses in CalculiX 0.20: Steady state dynamics randomly terminates without error - CalculiX
Fortunately, it should be fixed in the next release and is already fixed in a build posted in that thread on the CalculiX forum. Moreover, the Prool’s build was found to be working correctly too but compatibility mode had to be added to the new version of PrePoMax to support this build: A developer/preview PrePoMax version v1.4.0 has been released