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Nowadays, a lot of lock cylinders are translucent, and why, the main thing is that both sides of the lock cylinder are transparent, so you can see translucent.
Two of them are more likely. First, the lever of the lock cylinder is broken (there are also gears). The second is the dislocation of the lock body slot. >>>More
It may be a failure of the lock body, it is recommended to find a lock repair master from a professional store to check it.
Can you take a photo of your security door lock? Do you mean positioning the lock by lock rebound?
Who really repairs the lock cylinder, basically no one repairs it, because it can't be repaired, it's better to change it.
There is a screw under the square tongue that is not tightened, and it is OK to tighten it.