Proprietary information and corporate classified information do not exist once they are incorporated into the device and sold to the end user. That information now belongs to the end user, who will continue to need it even if the company is out of business, or refuses service to the owner of the device.
Any attempt to conceal that information from the end user should make the company liable for any failed repair performed by any individual, including harm arising from that failed repair. The only way to avoid that liability is to release all information to the end user, so they are fully informed when making a repair decision.
Yes, dangers exist from third party repairs.
Refusal or even simple failure to provide critical repair data to the end user or their agent denies the end user the ability to make an informed decision about repairs.
The company should be liable for all damages from a botched 3rd-party repair unless they provide to the end user complete specifications and unrestricted access to the device in order to make informed decisions about repairs.