This is because of sys_ticrate 0.01666667, which has other advantages though. The only reason why the laser worked so well all the time is that the projectile is delayed by one tic after shooting. But when reducing the ticrate, that delay is much lower, and regular laserjumps become impossible. This is why the secondary got added - to make the previous jumps possible again.
(Technical description: with less delay on the projectile, a forward-down laserjump hits BEFORE you pass the hit point, making it slow you down - with the high delay though, you can shoot angled down, and get past the impact point before the projectile explodes)
The decreased ticrate WILL happen, there is nothing that can be done about it as it's a game design decision by our game designer, LordHavoc. Plus, the lower ticrate DOES have lots of advantages (e.g. missing items when running fast through them much less often) - but this one disadvantage.