How to tension the chain when designing a lifter?

Among the automatic warehouse facilities, we designed and tested a vertical conveyor. During the test, the carriage sag was greater than expected. When the cargo enters the carriage, sag occurs, and when the cargo exits the carriage, it bounces up.
It is expected to be due to the chain sag. We are looking for a way to reduce the sag. We look forward to your opinions.
I will explain the equipment specifications. A geared motor + inverter was selected, and the fixed position is controlled by a sensor. The chain was selected as RS100*2 rows. The motor does not have an encoder, and the position is not controlled by a barcode. The cargo can be transported from 1 to 2.3 tons, and the speed can be controlled from 2.7 to 60 m/min.
The current design does not include a chain tension device, so we are trying to supplement it. I wonder if there is anything else to add. I would appreciate your good opinions.