Access error on NAS file system after about 10 minutes of inactivity

I have mounted some volumnes from a QNAP NAS system into my home directory via fstab:
//nas1/Sicherung_Alt /home/andreas/network/Sicherung_Alt cifs _netdev,defaults,vers=3,uid=andreas,gid=users,cred=/home/andreas/.config/nas1_andreas_cred 0 0
//nas1/Andreas /home/andreas/network/Andreas cifs _netdev,defaults,vers=3,uid=andreas,gid=users,cred=/home/andreas/.config/nas1_andreas_cred 0 0
//nas1/Bilder /home/andreas/network/Bilder cifs _netdev,defaults,vers=3,uid=andreas,gid=users,cred=/home/andreas/.config/nas1_andreas_cred 0 0
//nas1/Dokumente /home/andreas/network/Dokumente cifs _netdev,defaults,vers=3,uid=andreas,gid=users,cred=/home/andreas/.config/nas1_andreas_cred 0 0
//nas1/Hardware /home/andreas/network/Hardware cifs _netdev,defaults,vers=3,uid=andreas,gid=users,cred=/home/andreas/.config/nas1_andreas_cred 0 0
//nas1/Musik /home/andreas/network/Musik cifs _netdev,defaults,vers=3,uid=andreas,gid=users,cred=/home/andreas/.config/nas1_andreas_cred 0 0
//nas1/Software /home/andreas/network/Software cifs _netdev,defaults,vers=3,uid=andreas,gid=users,cred=/home/andreas/.config/nas1_andreas_cred 0 0
//nas1/Video /home/andreas/network/Video cifs _netdev,defaults,vers=3,uid=andreas,gid=users,cred=/home/andreas/.config/nas1_andreas_cred 0 0
//ASUS1/Test_Freigabe /home/andreas/network/Win10Test cifs noauto,_netdev,defaults,vers=3,uid=andreas,gid=users,cred=/home/andreas/.config/win10_andreas_cred 0 0

After booting Linux the access to the NAS files system works fine. But when there is no activity on the file system the mounts didn’t work any longer after about 10 minutes. The error message is: The NAS is down but this is not true.
When execute ls command within the mount root repeatedly with less than 10 minutes there is no problem.
When accessing one of the volumes for example by playing music from it this file system is not affected but all others get inaccessible even all of the volumes are located on the same disk in the NAS.
When a Windows computer is playing music from the NAS but Linux is not accessing it the file system gets nevertheless inaccessible.
Linux has no problem with a file system which is hosted on a Windows computer for test purpose. Also a Windows computer has no problem with the NAS.
When there is the file system outage uptime shows a higher load than normal which stays high. It can also effect other applications which did not use the NAS file system including reboot or shutdown via GUI (KDE). After reboot of the Linux computer the file system works fine again until it is not accessed for about 10 minutes.
I don’t see a setting in the NAS GUI like sleep after 10 minutes.
You can look more in detail about the tests in files info1.txt – info4.txt whereas messages.txt contains some system messages related to the file system.

Any idea what’s going wrong? Should I use other parameters in fstab?

info1: https://susepaste.org/3630430
info2: https://susepaste.org/48553965
info3: https://susepaste.org/71209004
info4: https://susepaste.org/94646264
messages: https://susepaste.org/9021074

It seems it is not possible to download the uploaded files from susepaste. Another try:
info1: https://susepaste.org/49776988
info2: https://susepaste.org/17089443
info3: https://susepaste.org/3060229
info4: https://susepaste.org/16082700
info5: https://susepaste.org/71801066
messages: https://susepaste.org/63665110