63 healthy m chronic back pain. Gr 1 spondylolithesis l34&l45+ facet arthritis. Bil facet blocks helped but still have bil butt pain. Advice?

Generally Good. Radiofrequency procedures work well if a previous facet injection or medial branch block was performed with greater than 75-80% relief that was obtained. As with anything there are failures, but quite low if the block worked well. Risks are the same as with any spine procedure, no different. Rare that you would be worse off afterwards.
Radiofrequency. If facet blocks helped radiofrequency neurotomy of medial branches may be a long-term solution.
Try it agian. You could try the facet injection again or we could try epidural block see if that help.
Options. Pain related to spondylolisthesis may be related to lateral recess stenosis, facet pain, central stenosis, discogenic pain or pain from the instability itself. There are multiple options to ascertain which of these is the most likely cause.