I'm the maintainer of the makemkv packages for gentoo and several users are complaining of segfaults with the following error:
makemkvcon[24345]: segfault at 0 ip 00007fcb08f36002 sp 00007fcae8f90868 error 4 in libfftw3f.so.3.3.2[7fcb08f36000+16e000]
I have not been able to duplicate it yet myself.