if the hop is fully on then the nub is pushing in too far for the bbs to get past, same thing happened with my cyma vss
looks like you may need to trim the lip on the rubber to eliminate any potential bbs catching on the lip
I used an asg ultimate m130 on mine and it fired out at 562fps on a .20, did the same thing as you and fitted a titan plus 18:1 gears and new compressions parts. standard V3 hop unit with ML 60, omega nub and standard 400mm inner barrel. changed to a m120 and dropped it to 490. with hop applied it fires .43s lovely and straight
I believe the battery goes in the suppressor on the LCT? on the cyma it goes in the stock, could the battery be pushing on your barrel maybe even with the spacer?