About Error of "clock overflow and run stoped"

I use two task executers of elevator.
During running, the error of "Clock overflow and running stop" happen.

So I searched the same error problem in this forum and found some isseus.
The answers are not 'to divide by zero speed'.
But in my case, the speed is not zero and so the answers of them can not be used to solve my owns.

I am using two elevators in same straight line.
The edge of elevator is running well in same condition but the intermediate elevator stops when entering items.

What's the problem?

I attach my model.

I am sorry for all.

I found what's the problem.

I set the global speed variable type (the value is 0.0009) to 'integer' not 'DOUBLE'.
So 0.0009 became zero.

Sorry again.