Birmingham’s Gavin made the short trip across the West Midlands to battle the fighting EBU welterweight title holder, live on BoxNation.
But a crippling body shot to the Brummie’s ribs which should have finished him off turned the tide in the sixth round, a late fightback proving futile despite both making it to the final bell.
A split decision went to the Italian veteran, 39, to make it a successful sixth defence of his crown after a belter of a contest.
It was supposed to be the crowning glory of Gavin, Britain’s only-ever world amateur champion, but instead came his first defeat for nine years in any code.
He set his stall out as he always does but Bundu bounced into action, although he was pegged back as Gavin loomed forward looking to land with precision punches.
Work-rate won Frankie the first round but Bundu responded with a clean left hook in the second, Gavin retorting with a right uppercut by the time the session was out.
They traded shots at will in the fourth with Bundu’s left hook this time stinging the body, only for Gavin to scramble his defences with another right uppercut that rocked his jaw.
Their mirror southpaw styles proved suitable for attacks to land and it rang true come the sixth, as Gavin hit the floor for only the second time as a pro. He looked out for the count after sinking face down as Bundu switched to connect with a right hook to the ribs, leaving mouths agape at the prospect of a clean finish.
The wily Gavin’s gumshield left his mouth in the process and forced a break, although he had answered the count with a split second to spare. The end seemed surely night. He lived to fight another round but came under fire again as blood leaked from his right eye in round seven, clinging on to see the eighth session.
A salvo began at the start as a left hook forced Bundu back but the champion took over until the 10th, where he had the upper hand. Gavin knew it as he threw the kitchen sink at him for the last two rounds, probably aware of the knowledge that it was likely to be too late. It went to the cards where Robert Verwijs had it 115-112 to Bundu, Arnold Bolger scoring it 114-113 in favour of the champion while Manuel Oliver Palomo had 114-113 to Gavin.