I reproduced it on 7.3-SNAPSHOT and I believe it affects 7.2RC1 also. Here's what I did:
- I built xwiki-platform-search-solr-ui XAR
- I took the latest XWiki 7.3-SNAPSHOT
- Start XWiki > Administer Wiki > Import > upload the Solr UI XAR > click Import with default options
- Main.SolrTranslations are listed in the XAR import tree so they are seen in the XAR
- After import, the "List of installed pages" lists Main.SolrTranslations multiple times (that's a different issue: the locale is not displayed) so apparently all translations have been imported
Check the Main.SolrTranslations page. You'll see that is has the content of the SK translations and the other translations are not present. My guess is that the translations are overwriting one another, probably because the document reference doesn't include the locale.