I'm also guessing that being picked-up & toted around was too ?invasive ? -- frequent? -- maybe he interrupted Raider when he was busy at some dog-activity, to carry him around, once too often? -
but those are just guesses.
Maybe Ur son could *ask* Raider if he wants to be carried - make it a 2-step process. ???
Squat down, pat yer thighs, & ask Raider to get up - if he does, carefully lift him up cradled against yer body, with his torso well-supported & a spread hand supporting his chest, with his forelegs going BETWEEN different fingers; GIVE HIM A HIGH-QUALITY, SMALL TIDBIT, & promptly squat to put him down on the floor again.
Build the duration of how long he's held as he develops tolerance, & watch very, very carefully for any sign of pain or discomfort - it could be that the way he's held
makes him uncomfortable, maybe the bony hock joints of his hind-legs are being bumped together?
Maybe he's being picked-up just after a meal, & his stomach is uncomfortable because it's full & being compressed or squeezed? -- I don't know, but there must have been more than 1 occasion when being toted wasn't enjoyable.
However, teaching him to enjoy it should be a simple matter, assuming he's not in pain or uncomfortable when he's held.