You don't state the exact model but on every oven I've ever fixed this problem on it's a broken door striker catch. Depending on your model, the catch will either be in the oven door or in the oven body; usually they're straightforward to replace but on older ovens spares can be almost as rare as dodo ****. Usually what breaks is a hardened tempered metal spring, so when they're not available as spares I can usually visit a local spring making company and get someone to make one up as a one-off using the fragments of the old one as a pattern. After the catch has been replaced the striker itself (usually a specially shaped pin) may need to be adjusted to engage correctly once more. Undoing the lock nut and screwing it in and out adjusts the depth, and is done after the striker catch has been adjusted side to side or up and down to meet the centre of the striker.
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You don't state the exact model but on every oven I've ever fixed this problem on it's a broken door striker catch. Depending on your model, the catch will either be in the oven door or in the oven body; usually they're straightforward to replace but on older ovens spares can be almost as rare as dodo ****. Usually what breaks is a hardened tempered metal spring, so when they're not available as spares I can usually visit a local spring making company and get someone to make one up as a one-off using the fragments of the old one as a pattern. After the catch has been replaced the striker itself (usually a specially shaped pin) may need to be adjusted to engage correctly once more. Undoing the lock nut and screwing it in and out adjusts the depth, and is done after the striker catch has been adjusted side to side or up and down to meet the centre of the striker.