diff --git a/core/src/main/java/google/registry/reporting/billing/CopyDetailReportsAction.java b/core/src/main/java/google/registry/reporting/billing/CopyDetailReportsAction.java
index 71ef70db9..2bfd4abf1 100644
--- a/core/src/main/java/google/registry/reporting/billing/CopyDetailReportsAction.java
+++ b/core/src/main/java/google/registry/reporting/billing/CopyDetailReportsAction.java
@@ -18,11 +18,12 @@ import static com.google.common.base.Throwables.getRootCause;
 import static google.registry.request.Action.Method.POST;
 import static jakarta.servlet.http.HttpServletResponse.SC_INTERNAL_SERVER_ERROR;
 import static jakarta.servlet.http.HttpServletResponse.SC_OK;
+import static java.util.stream.Collectors.joining;
 
 import com.google.cloud.storage.BlobId;
 import com.google.common.base.Splitter;
 import com.google.common.collect.ImmutableList;
-import com.google.common.collect.ImmutableMap;
+import com.google.common.collect.ImmutableMultimap;
 import com.google.common.collect.Iterables;
 import com.google.common.flogger.FluentLogger;
 import com.google.common.io.ByteStreams;
@@ -41,7 +42,6 @@ import jakarta.inject.Inject;
 import java.io.IOException;
 import java.io.InputStream;
 import java.util.Optional;
-import java.util.stream.Collectors;
 
 /** Copy all registrar detail reports in a given bucket's subdirectory from GCS to Drive. */
 @Action(
@@ -98,7 +98,8 @@ public final class CopyDetailReportsAction implements Runnable {
       response.setPayload(String.format("Failure, encountered %s", e.getMessage()));
       return;
     }
-    ImmutableMap.Builder<String, Throwable> copyErrorsBuilder = new ImmutableMap.Builder<>();
+    ImmutableMultimap.Builder<String, Throwable> copyErrorsBuilder =
+        new ImmutableMultimap.Builder<>();
     for (String detailReportName : detailReportObjectNames) {
       // The standard report format is "invoice_details_yyyy-MM_registrarId_tld.csv
       // TODO(larryruili): Determine a safer way of enforcing this.
@@ -145,17 +146,18 @@ public final class CopyDetailReportsAction implements Runnable {
     response.setStatus(SC_OK);
     response.setContentType(MediaType.PLAIN_TEXT_UTF_8);
     StringBuilder payload = new StringBuilder().append("Copied detail reports.\n");
-    ImmutableMap<String, Throwable> copyErrors = copyErrorsBuilder.build();
+    ImmutableMultimap<String, Throwable> copyErrors = copyErrorsBuilder.build();
     if (!copyErrors.isEmpty()) {
       payload.append("The following errors were encountered:\n");
-      payload.append(
-          copyErrors.entrySet().stream()
-              .map(
-                  entrySet ->
-                      String.format(
-                          "Registrar: %s\nError: %s\n",
-                          entrySet.getKey(), entrySet.getValue().getMessage()))
-              .collect(Collectors.joining()));
+      for (var registrarId : copyErrors.keySet()) {
+        payload.append(
+            String.format(
+                "Registrar: %s\nError: %s\n",
+                registrarId,
+                copyErrors.get(registrarId).stream()
+                    .map(Throwable::getMessage)
+                    .collect(joining("\n\t"))));
+      }
     }
     response.setPayload(payload.toString());
     emailUtils.sendAlertEmail(payload.toString());
diff --git a/core/src/test/java/google/registry/reporting/billing/CopyDetailReportsActionTest.java b/core/src/test/java/google/registry/reporting/billing/CopyDetailReportsActionTest.java
index c4b9568e2..b0ca522d4 100644
--- a/core/src/test/java/google/registry/reporting/billing/CopyDetailReportsActionTest.java
+++ b/core/src/test/java/google/registry/reporting/billing/CopyDetailReportsActionTest.java
@@ -178,21 +178,56 @@ class CopyDetailReportsActionTest {
     verify(emailUtils)
         .sendAlertEmail(
             """
-                Copied detail reports.
-                The following errors were encountered:
-                Registrar: TheRegistrar
-                Error: java.io.IOException: expected
-                """);
+            Copied detail reports.
+            The following errors were encountered:
+            Registrar: TheRegistrar
+            Error: java.io.IOException: expected
+            """);
     assertThat(response.getStatus()).isEqualTo(SC_OK);
     assertThat(response.getContentType()).isEqualTo(MediaType.PLAIN_TEXT_UTF_8);
     assertThat(response.getPayload())
         .isEqualTo(
             """
-                Copied detail reports.
-                The following errors were encountered:
-                Registrar: TheRegistrar
-                Error: java.io.IOException: expected
-                """);
+            Copied detail reports.
+            The following errors were encountered:
+            Registrar: TheRegistrar
+            Error: java.io.IOException: expected
+            """);
+  }
+
+  @Test
+  void testFail_tooManyFailures_one_registrar_sendsAlertEmail_continues() throws IOException {
+    gcsUtils.createFromBytes(
+        BlobId.of("test-bucket", "results/invoice_details_2017-10_TheRegistrar_hello.csv"),
+        "hola,mundo\n3,4".getBytes(UTF_8));
+
+    gcsUtils.createFromBytes(
+        BlobId.of("test-bucket", "results/invoice_details_2017-10_TheRegistrar_test.csv"),
+        "hello,world\n1,2".getBytes(UTF_8));
+    when(driveConnection.createOrUpdateFile(any(), any(), any(), any()))
+        .thenThrow(new IOException("expected"));
+
+    action.run();
+    verify(emailUtils)
+        .sendAlertEmail(
+            """
+            Copied detail reports.
+            The following errors were encountered:
+            Registrar: TheRegistrar
+            Error: java.io.IOException: expected
+            \tjava.io.IOException: expected
+            """);
+    assertThat(response.getStatus()).isEqualTo(SC_OK);
+    assertThat(response.getContentType()).isEqualTo(MediaType.PLAIN_TEXT_UTF_8);
+    assertThat(response.getPayload())
+        .isEqualTo(
+            """
+            Copied detail reports.
+            The following errors were encountered:
+            Registrar: TheRegistrar
+            Error: java.io.IOException: expected
+            \tjava.io.IOException: expected
+            """);
   }
 
   @Test