Videos not marked as watched

Videos do not get marked as watched. Even when I select “Mark as watched” from the Options menu, nothing happens. Can anybody help please?

Device: Rasp Pi B
Ram: 512
Installation media: SDcard
Connection: Wifi
Power Supply Type: USB charged
Peripherals: none
Storage Device: a Synology NAS, OSMC finds it under “UPnP devices”
OSMC version: I just downloaded it from the website yesterday so probably the latest one
Audio/Video Output: HDMI
Overclocked: No

This is what my video list looks like. I have seen some of these already but there is no mark.