Hi @Sylvain Lacombe ,

Preview Data button visible only CMDB 360/Multisource CMDB is enabled.

And can you remove filter condition for Rule#1 and try again. 

Lower priority rule will apply only if that is that is initial source created the record. and CI became stale based on the data refresh rules for the CI class will apply in next time only.

Please accept my answer or hit helpful if my solutions answer your query.
Thanks,

Swamy