I just saw this i the Veeam forum. After upgrading to version 9.5 of Veeam Backup & Replication, all jobs that has configured "active full" wil have the schedule reset to default (first Monday) for the "active full".
Veeam has reported this as a bug, and are working on a fix.
See the forum thread here: https://forums.veeam.com/veeam-backup-replication-f2/all-active-full-schedules-reset-with-9-5-t39349.html
Temporary fix: Document the settings for all jobs before upgrading and manual edit the jobs after upgrading.