Shadow copy problem

Hi all.
I have a problem with shadow copy on one client.
When it starts an image backup, it sends all SYSVOL (~12GB). When SYSVOL backup finished, it should start disk C backup, but does not.

Live log from server:
“|17.04.19 08:47 |DEBUG |Backing up SYSVOL…|
|17.04.19 08:47 |INFO |Starting scheduled full image backup of volume “SYSVOL”…|
|17.04.19 09:04 |ERROR |Error on client occurred: Error while reading from shadow copy device (1). Niepoprawna funkcja.| (Incorrect function)
|17.04.19 09:04 |ERROR |Backing up System Reserved (SYSVOL) partition failed. Image backup failed|
|17.04.19 09:04 |INFO |Time taken for backing up client xxxxxx: 16m 54s|
|17.04.19 09:04 |ERROR |Backup failed|
|17.04.19 09:04 |WARNING |Exponential backoff: Waiting at least 40m before next image backup|”

Client is 2.3.4 on windows 7
Server is 2.3.8 on debian 9

Other 30 clients backup with no problems so far.