When several LCD screen lifters are controlled together, some of them may not work synchronously or respond at all. You are able to solve this problem with following solution。
The lifters cannot work synchronously perhaps due to be out of the distance. You can send multistratum control order to solve it.
The lifters have no response because the control line can only work for limited lifters, otherwise part of the lifters cannot receive the control code. In this situation, the lifters can be divided into different groups for better control.
In addition, it is feasible to add a terminal resistance to RS485 control line of the first lifter.