Exiv2 use a hueristic to try and determine what the lens is. If you’re using an adapter, the adapter might be putting in some information that nudges exiv2 towards the wrong identification. Dark table gets this info from exiv2.
In 3.4 there is a “re-read metadata” button that’ll fix the problem.
The .exiv2 file is the right place to do that. dark table doesn’t really override what exiv2 gives it. The lens correction module will update as well.
Does the correction look good? Lens correction is done for a specific censor size with a specific lens.
Also if you update lensfun, this change will be lost. Lensfun provides a way for users to use their own correction data, it is safer to use that.