Most failures using any adhesive that is a pretty good choice for the application (like epoxy for shafts to inserts) is caused by lapses in prep, which we all can be guilty of since shaft to insert bonds need to be prepped so carefully by cleaning and sanding for best results.
As a woodworker/builder I have had to accept the fact that failures in glues are almost always caused by something I missed or didn't do- whether poor mixing, surface prep issues, or tempuratures during glue up. I wish I could blame the adhesives, but I rarely can.
Joshua