A loose towel bar can come from a loose set screw, a moving mounting plate, or a wall anchor that no longer grips. Before tightening blindly, identify which part actually moves. If the anchor hole has enlarged, driving the same screw tighter will not restore a solid attachment.
Check the small set screw first
Many decorative brackets attach to a hidden plate with a small screw underneath. Hold the bracket steady, tighten that screw with the correct tool, and see whether the movement disappears before taking anything else apart.
If the plate moves, inspect its screws and anchors
Remove the trim as designed and check whether the screws spin without gripping or the anchor pulls out of the wall. A sound screw into wood or a stud can be retightened; a failed anchor needs replacement with one suited to the wall material and load.
Do not reuse a blown-out hole without repairing it
Anchor type matters in drywall, plaster, or masonry. If the material around the hole is broken, repair the substrate or relocate the fastener into sound material while respecting the bracket spacing. A new anchor in crumbling material will still be loose.
Reassemble and test with a moderate load
Tighten until the bracket is secure, not until the plate bends or the anchor strips out. Hang a normal towel and confirm there is no rotation. If the wall is damp, soft, or damaged, correct that problem before relying on the attachment.