From #2680

• Lookup DOI action for the button is not in a separate thread (ugly but present long time ago)
• GUI freezes when exception from above is catched. Maybe related to the start inside the FX thread 9b28d36. Also @lynyus reported that the whole GUI stopped working for him, so maybe this also triggers the freeze problem here and we need to fix the sart in FX thread method somehow.
• Error in CrossRef (500) Various problems accessing the CrossRef API CrossRef/cayenne#5: This happens randomly!
  http://api.crossref.org/works?query.title=A+break+in+the+clouds%3A+towards+a+cloud+definition&rows=20&offset=0 ->

{"status":"error","message-type":"exception","message-version":"1.0.0","message":{"name":"class java.lang.RuntimeException","description":"java.lang.RuntimeException: Solr returned a partial result set","message":"Solr returned a partial result set","cause":null}}

• Error in Crossref 503 & 504
  maybe log to the console and in the status bar for the user that the service is unavailable.
  Follow up Consistent methodology to signal that service is not available for fetchers #2729