Updating SH through WUfB - mixed results

Hello,

Can I have your opinion on the best way to update the surface hub ?
At the moment, all our SH are enrolled in WUfB.
You can see the settings for the Ring in the attached screenshot.
The problem is this policy is deployed for months now and our SH's are still not all at the same level.
For example, according to MEM, we have for feature update version:
1703, 5 devices
20H2, 74 devices
Latest, 26 devices

And for the quality update version :
10.0.15063.2679 5 devices
10.0.19042.1526 1 devices
10.0.19042.1586 4 devices
10.0.19042.1645 35 devices
10.0.19042.804 34 devices
10.0.19043.1645 7 devices
10.0.19043.867 1 device
10.0.19044.1237 1 device

Internet connection on these machines are OK.
The maintenance window configured througha device configuration profile starts at 08pm with a duration of 5 hours.

How is this possible that the machines are still not updating ?
We would like to avoid sending people all around the country to update these devices.

Is there something wrong with our Update ring configuration ?

Thanks in advance for your help.

Marc