When moving over to CMAKE build system, we somehow assumed that in order to use RTSPEC we needed both libcrypt and libuuid. Looking at the code this does not seem to be nessicary, with the general preference being to using libcrypt.
Because of this check in the build-system, SaC would sometimes not build with RTSPEC (even if libcrypt is present on the system) meaning that it would use a simple (broken?) varient of RTSPEC.