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Anything with a double beveled edge is likely to damage the bead or frame, as it's the leverage of the single bevel sharp edge being of to one side that's needed.
Properly sharpened like a chisel, a painters tool should work, but they are a bit too wide for some of the really tight beads. It may come in handy as a second knife if the bead keeps snapping back into place.
Have the flat face of the knife towards the panel and press/gently hammer it into the non existent gap.
It may only go in a mm or so and probably not free the bead at that point. Then use the heel of the bevelled edge to lever the bead hook free. Use a second tool to work outwards if needed.Some of the flat angled beads are bastards.
Cheers for the advice. I tried last night with a painters tool but got nowhere - The tool was too thick and that beading was on tight!