The problem is that the star positions change over time via galactic orbit. 'Oumuamua's trajectory appears to originate from Vega, but Vega would have been at a

The problem is that the star positions change over time via galactic orbit. 'Oumuamua's trajectory appears to originate from Vega, but Vega would have been at a different position in relation to our solar system back when 'Oumuamua was at the same distance from the Sun as Vega.