The constant mesh 6-speed transmission in the V4 uses engagement dogs that protrude from the sides of the pinion gears and engage into the rotating wheel gears.

Over time the engagement dogs will wear or round-off, so the total engagement contact surface is reduced. Speed shifting and/or not getting it all the way into 2nd accelerates the wear. The first to second shift is the longest throw in the transmission. You are moving the same pinion gear out of first, through neutral, then into second.

The popping out problem often starts as a ratchetting effect in and out of gear, where the shift fork tries to hold the gear in position but ultimately fails. Once the shift fork or groove it fits into wears, the problem advances to popping out of gear and into a false neutral under acceleration.

The repair requires replacement of all the worn gears and forks, or a machining process called a gear undercut can be used to restore the contact surfaces by cutting a reverse angle in the engagement dog and mating wheel gear slot. The undercut service provides a long term repair because the gears draw together once the initial engagement occurs. The machining process is usually much less costly than buying new gears.