Hi Amine Le,
I have tested the SmartGantt Chart component in a similar use case as from the information that you have shared.
However I was unable to reproduce the issue that you mention that’s why I would suggest is to create a code example which reproduce the issue in order to be able to give you a solution about it.
Please, do not hesitate to contact us if you have any additional questions.
Best regards,
Yavor Dashev
Smart UI Team