What i did: i first formatted the SD card with SD formatter. Then used diskpart to clean it intirely, using this tutorial https://www.[Suspicious link removed]s/www.windowscentral.com/how-clean-and-format-storage-drive-using-diskpart-windows-10%3famp
After that i could write the X10 file to the SD card succesfully. Put it in one of the baikals.....and tadaaaaa!! It's working again!
Thanks for your help. Tomorrow i will do the same with the rest of the baikals and give an update when they are all on air.
great! when you formated sd card, which file allocation system did you use? fat32, ntfs or some other?