I would suggest change the primary group of the user chris like this
```lang-shell
usermod -g users chris
```
This will change the primary group of `chris` from `chris(1035)` to `users(100)`

As I have no idea on how samba is configured, that is all I can suggest, you can always switch back to original config as follows.
```lang-shell
usermod -g chris chris
```
Also ensure that user logs out and log in again after you make any changes in the groups.