Nextcloud 16.04 error external storage smb/cifs mariadb: Aborted connection to db

I am running nextcloud 16.04 on a centos 7 with mariadb 10.4.7 .
When configuring the external storage app to my smb/cifs Server the Connection are aborted after

several minuites with , Server Connection lost, in the gui. In my mariadb.log, [Warning] Aborted connection 266 to db: ‘nextcloud’ user: ‘nextclouduser’ host: ‘localhost’ (Got an error reading communication packets). After a short period I can handel the files on the smv/cifs share again.
Can you give a hint to solve the Problem?

This is the apache error_log entry : child pid 4303 exit signal Aborted (6), the same time when “Server Connection lost”. When I do a refresh in the gui I can handle the files on the share again.