as these internal coils are used more often (copy pasted as I understand), is it maybe possible the software shows a "end of program scan" state instead of an, as expected, "current" (at shown rung) state?
Yes, the way the scan works is the X inputs and Y outputs are read from/written to at the end of the scan. So regardless if the state of your C1821/C1822 after the Y coils were set, they will be ON at the end of the scan. Of course, only if the C1821/1822 coils were set BEFORE this rung.