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You might be able to repair the keyboard, or not. If it is a corroded trace, there is quite a lot of effort to disassemble the keyboard, and will require a bolt mod to put it back together again. Which will probably require to to buy a few more parts.
On the other hand, if $25 is not too much money, then you will have a whole keyboard of spare parts. If you find another Model M that works but is missing keycaps, say, you can transfer the missing keycaps from the broken keyboard to the working one. Or the controller. Or case.