Unfortuantely the only person actually qualified to work on Lore to see what was "wrong" with him is Dr. Soong and he was dead.
(If I do recall, it was Soong's plan to get back to Lore to try and to mend his personality quirks but couldn't before the colony had to be evacuated.)
And we don't know that Lore's body wasn't sent to Star Fleet, perhaps Maddox, for study with the implicit condition that Lore not be re-assembled/re-activated.
It may be possible to reactivate Lore's head, and leave his body disassembled. I don't remember if Data could control his body parts with his head unattached, but just in case the body parts could be stored in separate locations, at different facilities, with no one cybernetacist knowing the locations of all the parts, and the ones working with Lore's head would have no knowledge of where the parts are or of those who know any parts location. Yeah, it's overkill, but with Lore you can't be too careful. He could be studied safely, and perhaps fixed.
Other security measures could be: doors with a handle, full body scan that will unlock the door only if no cybernetic parts are detected, Lore's head facing away from the door, and in a box that'll allow for no movement of his head, battery power source, computer systems in the lab that are not hooked up to the main frame of the rest of the facility and that also require a body scan to operate, the computers in the room are not connected to environmental control (in essence the computer in the lab is completely isolated), the room is shielded from tricorder scans either entering or exiting the facility even when the door is open (Maybe even do away with the door and have only transporter access from the outside) and the computers, and any device brought into the lab, have no voice interface
Yes, it's all overkill, but Data has shown that he can interface with Federation computers through his head and can mimic voices. So, any possible way for Lore to take control of the lab, or piece of equipment, must be accounted for.
Damn, I
AM a geek.