Custom application is being deleted

We have a “simple” application to manage APNs and keep the modem connected on more than a hundred of devices. On a handful of them, the application keeps being deleted from time to time and the devices go offline.
Why is the application being uninstall/deleted?
And why only on a very small number of devices?
They are all the same FX30 model with the same Legato version (18.06.1)

how did you update your application?
There is rollback mechanism if there is too many reset within probation period:

Thank you so much. The mystery is solved. The problem was actually outside of the FX30, another script resetting the modem way too often.
The threshold is pretty low in the probation period before the rollback.