Hi,
PUBLIC Role provides access to required objects in _SYS_REPO Schema, so I don't advise granting SELECT on the whole _SYS_REPO Schema.
When you execute a data preview from a node in a HANA View, you will generate a new Column View in the _SYS_BIC Schema, which will provide requested data. Here, depending on the rights you have on _SYS_BIC Schema and if this Column View has been generated by other user already, you may find this error.
This Column View ends always with /dp/<node name> and from a security perspective it is secured to be accessed only by the user that has created. Therefore, if another user tries to read data from this Column View will get this "Cannot open Data Provider" error.
The solution is granting CREATE ANY & DROP in _SYS_BIC Schema, so any user can drop any existent Column View of this type and generate his own one. The process will be transparent for the user.
By default, MODELING Role has full rights on _SYS_BIC schema, so using this Role will work too; although it grants far more privileges.
Regards,
Joaquín