many "Logon Failed" messages when Backup a Network Share (acronis tries service logon instead plan credentials)

Acronis Agent 1 -> "Acronis Managed Machine Service" runs as "Company\Acronis" (Domain User)
server 2 -> just a regular windows server providing a network share

Now I created a backup plan for "Acronis Agent 1" to backup a network share \\server2\share. When creating the Plan I have to supply credentials for the plan and after that i can select which files/folders I want. Until here everything works just as it should. Acronis starts the backup plan on "Acronis Agent 1" and end successful.

When you look in the event viewer on server2, you can see that acronis constantly tries to connect as "Company\Acronis" (Domain User) and produces a huge amount of "An account failed to log on." audit messages. Thats strange because after some wrong tries it uses the correct (the specified) credentials from the plan and the backup is successful.

Why is Acronis trying to use the Service Credentials from the Agent in the first place (and multiple times until the backup is finished) instead of only the correct ones i specified in the plan during creation?