Running crontab sync job completely in the background on Ubuntu

[Abdolaziz]

My system
OS: Ubuntu Impish
FreeFileSync version: 11.14 (installed directly from this website)
I use this command to run my sync job automatically (unintended in the background).
Command:
0 */6 * * * DISPLAY=:0 /opt/FreeFileSync/FreeFileSync /home/PF/PF.ffs_batch

When the command runs by crontab, the icon (not the full window or any dialogue) of FFS appears on my taskbar while syncing, then disappears. On my previous Ubuntu 21.4, I hadn't this problem and the crontab used to run completely hidden.
Any help please.