diff --git a/dspace-api/src/main/java/org/dspace/util/SolrImportExport.java b/dspace-api/src/main/java/org/dspace/util/SolrImportExport.java
index df34454a40..387198c0fb 100644
--- a/dspace-api/src/main/java/org/dspace/util/SolrImportExport.java
+++ b/dspace-api/src/main/java/org/dspace/util/SolrImportExport.java
@@ -247,14 +247,18 @@ public class SolrImportExport
 			swapRequest.setAction(CoreAdminParams.CoreAdminAction.SWAP);
 			swapRequest.process(adminSolr);
 
-			// export all docs from now-temp core...
-			exportIndex(tempIndexName, exportDir, tempSolrUrl, timeField);
+			// export all docs from now-temp core into a temporary directory...
+			String tempExportDirName = ConfigurationManager.getProperty("dspace.dir") + File.separator + "temp" + File.separator + "solr-data-tmp";
+			exportIndex(tempIndexName, tempExportDirName, tempSolrUrl, timeField);
 			// ...and import them into the now-again-actual core *without* clearing
-			importIndex(tempIndexName, exportDir, false, origSolrUrl);
+			importIndex(tempIndexName, tempExportDirName, false, origSolrUrl);
 
 			// commit changes
 			origSolr.commit();
 
+			// delete temporary export dir
+			FileUtils.deleteDirectory(new File(tempExportDirName));
+
 			// unload now-temp core (temp core name)
 			CoreAdminRequest.unloadCore(tempIndexName, false, false, adminSolr);
 
@@ -331,6 +335,8 @@ public class SolrImportExport
 			return;
 		}
 
+		Arrays.sort(files);
+
 		for (File file : files)
 		{
 			log.info("Importing file " + file.getCanonicalPath());
@@ -443,8 +449,18 @@ public class SolrImportExport
 		query.setRows(0);
 		query.setGetFieldStatistics(timeField);
 		Map<String, FieldStatsInfo> fieldInfo = solr.query(query).getFieldStatsInfo();
-		Date earliestTimestamp = (Date) fieldInfo.get(timeField).getMin();
+		if (fieldInfo == null || !fieldInfo.containsKey(timeField)) {
+			log.warn("Cannot get earliest date, not exporting index " + indexName + ", time field " + timeField + ", from " + fromWhen);
+			return;
+		}
+		FieldStatsInfo timeFieldInfo = fieldInfo.get(timeField);
+		if (timeFieldInfo == null || timeFieldInfo.getMin() == null) {
+			log.warn("Cannot get earliest date, not exporting index " + indexName + ", time field " + timeField + ", from " + fromWhen);
+			return;
+		}
+		Date earliestTimestamp = (Date) timeFieldInfo.getMin();
 
+		query.setGetFieldStatistics(false);
 		query.clearSorts();
 		query.setRows(0);
 		query.setFacet(true);