so please, get a joy con rail and try to fix it yourself.. or have someone familiar with such stuff do it for you.
You know how keen Nintendo are on hacking stuff right? can't risk getting your switch getting ipatched for something such as a joycon rail.
if you can't replace it in the end then simply leave it as is and play on the dock instead of portable.
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While that might be true, hence they cannot patch a ROM chip, unless they got the needed tools to defy the laws of electronics and computing lol.
least they could do is replace the motherboard.?