I have tried both 1.6.1 and also the original 1.6 with original RDB.
Ken Griffey Jr.'s Slugfest (U) seems to be unsupported by TR64 OGL:
r4300i: 0.1%
Dlist: 0.0%
Alist: 0.0%
Idle: 99.9%
Can someone please test this and verify if it is the same for you?
Or if you have it working tell me your settings or (Emulator)