Hello,
The problem must come from the end date in the file. It is the same as the start date.
BEGIN:VEVENT
DTSTART;VALUE=DATE:20241225
DTEND;VALUE=DATE:20241225
DTSTAMP:20240101T000000Z
SUMMARY:Jour de Noël
UID:a2ad4bde5f021604f088ac8ff9dd8fd0
END:VEVENT
By changing end date = start date + 1 day, it is ok
Régis