Why is my arched oak door sagging away from the jamb every time I let go?

The issue is almost certainly a combination of hinge layout and insufficient structural backing behind that arched jamb. Double-action hinges are notoriously finicky with heavy oak and reeded glass because they have multiple pivot points that allow for 'play' which you don't get with a standard butt hinge. If the top of the door is pulling away the second you let go, your top hinge is likely taking 80% of that cantilevered load and the jamb is twisting or the screws are just pulling through the soft wood behind it.

Since you still have the drywall off, you need to reinforce the framing immediately. Standard 2x4 blocking isn't enough for a door this dense. I'd recommend sistering a **LVL or a steel plate** behind the pivot side of the arch to ensure the frame cannot flex even a fraction of a millimeter. You also need to check if those hinges are 'biased' towards the top. For a heavy door like this, you shouldn't have even spacing. You want two hinges near the top to fight that gravity pull and one at the bottom. Check the weight rating on those silver hinges too. Many of the standard ones you find at hardware stores max out at 75-100 lbs, but a solid oak door with thick reeded glass can easily push 150 lbs or more. If you're over the limit, those hinge barrels are actually bending under the tension. You might need to swap them out for heavy-duty floor-mounted pivots or commercial-grade double-acting spring hinges that can actually handle the foot-pounds of torque being applied to that top corner.

Finally, make sure you are using **long structural screws** that go through the jamb, through your shims, and at least 2.5 inches into the actual wall studs. If you're just screwed into the oak jamb itself, the weight of the glass is just going to keep pulling that jamb away from the rough opening. Shimming an arch is a nightmare because you can't easily wedge it, so I usually use solid plywood blocks cut to the radius of the arch to ensure there's zero void between the jamb and the framing.

Spot on about the steel backing. I had a similar oak arch job last year and even with LVLs, we still saw a hair of movement untill we addressed the screw bite. One thing people often overlook on these heavy double-action setups is the screw gauge itself. If you're using the standard #10 or #12 screws that came in the hinge box, they can actualy shear or stretch slightly under that much oak and glass. I'd jump up to a #14 or even a 1/4-inch timber bolt if the hinge leaf can be bored out to accept it. That extra diameter prevents the 'sag' you get from the screw shank slightly bending inside the pilot hole.

You need to ditch those stock silver hinges and pick up some Bommer 3029 double-acting spring hinges. They are the only ones I trust for heavy oak installs becuase the steel is hardened and won't flex like the cheap hardware store stuff. If that door is over 100 lbs, make sure you get the 8-inch version. I'd also swap out those standard screws for GRK RSS Structural Screws. They have a built-in washer head that bites into the oak and the LVL backing without snapping, wich will stop that top corner from pulling away from the jamb for good.

Have you ruled out the moisture content of that oak before you start ripping the framing apart? If the wood was still a bit green when it was milled for the arch, you might just be seeing it settle and pull. Also, I'm curious about the floor—is it a slab or a joist system? Even if the jamb is rock solid, I've seen heavy oak doors like this cause the floor itself to deflect just enugh to throw the top of the arch out of plumb. Might be worth putting a laser on the floor to see if it's dipping when the weight hits.

Forget the spring hinges for a second and look at your floor. Back in the day, we wouldn't trust a jamb to hang that much oak and glass alone. You need a heavy-duty floor pivot, the kind that lets the floor take the weight instead of the side jamb. I remember fighting a 200-pound beast in '84; we had to mortise a Rixson pivot into the subfloor and tie it right to the joists. If you're hanging that off the wood alone, gravity is gonna win every time, I don't care how many structural screws you drive in.