diff --git a/app/src/main/java/org/fdroid/fdroid/Preferences.java b/app/src/main/java/org/fdroid/fdroid/Preferences.java
index 0e9e4f2b6..5ae92b09a 100644
--- a/app/src/main/java/org/fdroid/fdroid/Preferences.java
+++ b/app/src/main/java/org/fdroid/fdroid/Preferences.java
@@ -594,7 +594,7 @@ public final class Preferences implements SharedPreferences.OnSharedPreferenceCh
         return output;
     }
 
-    private String intMapToString(HashMap<String, Integer> intMap) {
+    private String intMapToString(Map<String, Integer> intMap) {
         String output = "";
         for (String key : intMap.keySet()) {
             Integer value = intMap.get(key);
@@ -612,7 +612,7 @@ public final class Preferences implements SharedPreferences.OnSharedPreferenceCh
         return output;
     }
 
-    private HashMap<String, Integer> stringToIntMap(String mapString) {
+    private Map<String, Integer> stringToIntMap(String mapString) {
         HashMap<String, Integer> output = new HashMap<String, Integer>();
         for (String line : mapString.split("\n")) {
             String[] pair = line.split(" ");
@@ -646,12 +646,12 @@ public final class Preferences implements SharedPreferences.OnSharedPreferenceCh
         return preferences.getBoolean(PREF_PREFER_FOREIGN, false);
     }
 
-    public void setMirrorErrorData(HashMap<String, Integer> mirrorErrorMap) {
+    public void setMirrorErrorData(Map<String, Integer> mirrorErrorMap) {
         preferences.edit().putString(PREF_MIRROR_ERROR_DATA, intMapToString(mirrorErrorMap)).apply();
     }
 
-    public HashMap<String, Integer> getMirrorErrorData() {
-        HashMap<String, Integer> mirrorDataMap = new HashMap<String, Integer>();
+    public Map<String, Integer> getMirrorErrorData() {
+        Map<String, Integer> mirrorDataMap = new HashMap<String, Integer>();
         String mapString = preferences.getString(PREF_MIRROR_ERROR_DATA, "");
         if (mapString == null || mapString.isEmpty()) {
             // no-op, return empty map to avoid null issues
diff --git a/app/src/main/java/org/fdroid/fdroid/net/FDroidMirrorParameterManager.java b/app/src/main/java/org/fdroid/fdroid/net/FDroidMirrorParameterManager.java
index 7d8f22234..4716683c9 100644
--- a/app/src/main/java/org/fdroid/fdroid/net/FDroidMirrorParameterManager.java
+++ b/app/src/main/java/org/fdroid/fdroid/net/FDroidMirrorParameterManager.java
@@ -11,29 +11,32 @@ import org.fdroid.fdroid.FDroidApp;
 import org.fdroid.fdroid.Preferences;
 import org.fdroid.fdroid.data.App;
 
+import java.util.Collections;
 import java.util.HashMap;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
 import java.util.concurrent.Executors;
 import java.util.concurrent.ScheduledExecutorService;
 import java.util.concurrent.TimeUnit;
 
 public class FDroidMirrorParameterManager implements MirrorParameterManager {
 
-    private volatile HashMap<String, Integer> errorCache;
-    private static final int DELAY_TIME = 1;
+    private final ConcurrentHashMap<String, Integer> errorCache;
+    private static final int DELAY_TIME = 5;
     private static final TimeUnit DELAY_UNIT = TimeUnit.SECONDS;
     private volatile boolean writeErrorScheduled = false;
-
-    private final Runnable delayedErrorWrite = () -> {
-        Preferences prefs = Preferences.get();
-        prefs.setMirrorErrorData(errorCache);
-        writeErrorScheduled = false;
-    };
-
+    private final Runnable delayedErrorWrite;
     private final ScheduledExecutorService writeErrorExecutor = Executors.newSingleThreadScheduledExecutor();
 
     public FDroidMirrorParameterManager() {
         Preferences prefs = Preferences.get();
-        errorCache = prefs.getMirrorErrorData();
+        errorCache = new ConcurrentHashMap<String, Integer>(prefs.getMirrorErrorData());
+        delayedErrorWrite = () -> {
+            Map<String, Integer> snapshot = Collections.unmodifiableMap(new HashMap<String, Integer>(errorCache));
+            Preferences writePrefs = Preferences.get();
+            writePrefs.setMirrorErrorData(snapshot);
+            writeErrorScheduled = false;
+        };
     }
 
     public void updateErrorCacheAndPrefs(@NonNull String url, @NonNull Integer errorCount) {
diff --git a/app/src/test/java/org/fdroid/fdroid/PreferencesTest.java b/app/src/test/java/org/fdroid/fdroid/PreferencesTest.java
index 2eaf48e4a..7d1fa55e9 100644
--- a/app/src/test/java/org/fdroid/fdroid/PreferencesTest.java
+++ b/app/src/test/java/org/fdroid/fdroid/PreferencesTest.java
@@ -166,7 +166,7 @@ public class PreferencesTest {
         Preferences preferences = Preferences.get();
         // serialize an empty map
         preferences.setMirrorErrorData(new HashMap<>(0));
-        HashMap<String, Integer> result = preferences.getMirrorErrorData();
+        Map<String, Integer> result = preferences.getMirrorErrorData();
         // deserializing should return an empty map without throwing any exceptions
         assertNotNull(result);
         assertEquals(result.size(), 0);