I’m 6’1 34” inseam. My 58 cm bike is set up where I feel comfortable on long rides, but I’m still getting some handlebar back and forth twitch while switching gear (downtube friction) or shifting hand positions.

It’s telling me something isn’t balanced. Would a longer stem and lowering the bars, or the reverse of that help make things rock solid?

Seat is set back almost to max, seat to bar drop is maybe 5-6 cm. I haven’t measured it since I last adjusted