My 350z convertible top will not seat down on the trunk in the final stage , has a 1/4 inch gap.

Lubricate every single part that moves in the top frame all the hinge points, use a light oil like 3 in1. Wipe off the excess do not get it on the interior trim like seats and door panels. Move the top up an down a few times to work the oil in and then try putting it all the way down. Good luck

1. You either have a section of rear seat that folds down or you don't. Most cars do and those vehicles will have a manual tab just behind the seat that is connected to a cable that will release the trunk lock unless the lock is broken. So check the top of your rear seat sections for release buttons that enable a section of seat to be folded down. Then look just inside the opening for the manual cable release.

2. If you have a car with no section of rear seat that can be folded down, you will have to unbolt the rear seat to get access to the trunk. You need to remove the bottom section of the seat first. This will just pull up from the front and you can remove it from the car. Then you should be able to access the bolts that hold the upright section of seat in place.

ok make sure there is nothing stopping it like a arm that is part of the frame sometime the rivet come lose or rot off,or the motor may be on its way out

Door lock issue could be several things. The switch is usually the cause, but the relay could also cause this. The convertible top is usually the relay in the trunk. It is on the upper area of the rear seat, in the middle of the trunk. Replace it. I have replaced them before, and the new relay did not work. I re-wired some of these with two relays. One for up control and one for down control. Have fun.

The same thing happened to my car and the dealership had to replace the entire top. I think it was a problem with the frame.

Did you ever find a solution?

You are probably low on fluid.
The reservoir is probably behind the rear seat with the motor/pump.
Fill it with ATF with the top down. Cycle it a few times and fill it again, always with the top down. Keep doing that till the reservoir accepts no more fliud.
While you have things apart look for leaks along the lines and cylinders.

The engine has to be running the parking brake set if stick shift or in park if auto. and your foot hasto be on brake.

top still needs to be adjusted to fully seat properly in the trunk/boot. if the upholsterer who replaced the top is not familiar with the adjusting process for a BMW, then i would take it to a BMW dealer and have them do the final adjustments.

make sure your car is in park and that you have your foot on the break....if you release your foot it will stop. So keep your foot on until it is fully open or fully closed and the passenger seat has returned to where you had it set prior to opening or closing