My custom ILS not work anymore after SU4

[SimoG6]

the world of FS is governed by the geographic north (from what I understand). Perhaps this is the missing data

In fact, if you draw and align the runway to that drawn on the satellite photo, it will not have the heading of the charts but the one respect to the geographic north. Eg. this is the value FS gave me for the runway: 285.32699 (I aligned it by eye) on the charts is 284.

[Downscc]

You are confusing magvar with longitude, which is negative West. However, magvar has always been negative East. The memory aid I learned in pilot training in the 1970’s was, “East is least, West is best.”