Main contactor releasing during drive

Hie guys.

I have just finished a degree in electrical engineering and I am still new and fresh to the elevator industry.I am having problems fixing an elevator I am working on .Its displaying the KONE fault code 0036 .When going up directly NON STOP from ground to 12th and final floor it's working perfectly fine.Even going up while stopping at different flows it's working perfectly fine.

The problem is coming when going down. It only works perfectly fine if you are stopping at very floor. The moment you try to bypass 3 or 4 or 5 floors or car call from 12th floor directly to ground ....the main contactor is being released during drive and the elevator is stopping immediately.

How do I address this issue.Please help. .thank you

Check that you are not clipping a hall lock? Maybe bad self closer on one of those hall doors and when elevator and CW meet in the middle the air pressure is breaking the lock contact? Hoistway selector tape is clean and aligned to the tape head. No flags on tape were moved?
It is a fault 36 and not 26 because a 26 fault usually means drive is toast.

Check encoder connections. Check set screw on encoder wheel.
Check that iencoder grounded.
Check all terminals on drive and cpu

What controller? Miprom21?

Seems the controller can’t “look ahead”. No prints on the job? If not, your gonna have a tough time. If so, start scouring the down direction circuit. D, DX, SD or whatever is in the down circuit.

Like Turbo asked; “what controller?”. If it’s a Miprom 21, check the encoder coupling. Loose set screws, broken spring type couplers will seem fine in one direction but give grief in the opposite. Faults will be generated on an encoder problem. Or, as was mentioned the encoder itself, but rule out other possibilities first.

Kinda sounds like it’s seeing floor positions when it’s not supposed to. On a more than one speed run see if car is rolling back and your getting a double blip on first floor as it takes off. Try slowing down the acceleration. Like your 61 30 on off and on again before it reaches
The next floor. There is supposed to to be rope compensation weight installed . They normally get thrown out . Problem I have had before
Had to add weight to car and rebalance. Ropes not biting in undercut
Enough and car will slip coming down especially near the top half of shaft same thing if you increase I and p factor car will go into pit empty. Weight and acceleration / deceleration. Goood luck

Also check encoder and tach. Watch 4-30-1 and 4-31-1 for variation in feedback I’m guessing kcm with a v3f25