Hi Trangtun, welcome to our Forum!
This is a known issue (point order in the frame exports is not consistent)- and it will probably be solved in the next release- now planned for Q1 2021.
That said- when exporting frames you will lose some design information (you are reducing a complex DELFTship model file to a limited text file) so when importing a set of stations the shape is likely not going to be exactly what you exported.
Thank you very much for your information. I’m glad to be one of Delftship learner.
As you said, is it impossible to fix that issue? So I should choose the different way to built the surface from offset table? Look forward for your reply, thank you in advance!