Did you read our documentation http://xstore.helpscoutdocs.com/article/30-base-theme-translation ?
If you want to avoid the problem with translation you can place translation files into wp-content/languages/theme folder and use theme prefix, for example, xstore-en_GB.po, xstore-en_GB.mo.
Also, you need synchronize translation files after update the theme. Button Sync (Loco Translate plugin http://xstore.helpscoutdocs.com/article/30-base-theme-translation) allows you to synchronize your translation file with updated pot file. It means if we made any changes in template files that may affect transaltion or we added new string for the translation and you updated theme you need to synchronize your translation with updated files. Only after synchronization you’ll be able to translate new strings or strings that were changed. You may lose only strings that were changed.
