Form: very weird reset

Hi,
In my app (a sort of basic CRM), I have several forms (client, contact, mission…) in various screens.

For some of them, the form is “reseted” when I open it: while I structured it with a few questions (+ UI), at a point in time, the form appears with its original format and above all linked to an other tab.
nb: I don’t manage to reproduce the issue.

More concretely:

BEFORE

AFTER

Do you have any clue?
Thanks in advance