Data gets corrupted when same module is used by 2 users with same credentials and turning from offline to online



I am developing an android application using ROS and i ran into a problem as follows:
Data gets corrupted when same module is used by same users on different devices simultaneously in offline mode.Then turning both the devices from offline to online at the same time makes the data corrupted when it is synced and seen on ROS.
There is a table for coordinates which shows no. of coordinates.Usually data is shown as "4 Objects"or “5 Objects” but in this situation described above the already existing manipulated data turns into “0 objects”.This is the case with 2 users but with 1 user the I am not able to reproduce the scenario Can anyone help me with this situation that why data is corrupted certainly in 2 user case and uncertainly in 1 user case.