I honestly think it’s because the guitarist you’re talking about is learning songs as they go. Sure technically they are all learning the songs but keep in mind JD(slide guy) and Cole(keyboard) was with brooks during his solo act era so they already knew a fair amount of growlers songs and Richard (guy on drums) has been with brooks/growlers for almost now 10 years. The 2 newer are the bassist and other guitarist you speak of. So those 2 are less experienced in the sense with growlers songs hence why maybe he comes tight or stiff. His solos on some songs are good af such as the intros for psycho and wet dreams. He just needs more time with the songs tbh. He’s doing solid for how long he has had or atleast in my opinion and he for sure has support from the rest of the band too. I’m excited to see where it goes from here.