diff --git a/src/Machine/test/Serval.Machine.Shared.Tests/Services/PreprocessBuildJobTests.cs b/src/Machine/test/Serval.Machine.Shared.Tests/Services/PreprocessBuildJobTests.cs
index 442cb06a..74e5031c 100644
--- a/src/Machine/test/Serval.Machine.Shared.Tests/Services/PreprocessBuildJobTests.cs
+++ b/src/Machine/test/Serval.Machine.Shared.Tests/Services/PreprocessBuildJobTests.cs
@@ -65,7 +65,7 @@ public async Task RunAsync_TrainAndPretranslateAll()
 
         await env.RunBuildJobAsync(corpus1);
 
-        Assert.That(await env.GetPretranslateCountAsync(), Is.EqualTo(4));
+        Assert.That(await env.GetPretranslateCountAsync(), Is.EqualTo(2));
     }
 
     [Test]
@@ -76,7 +76,7 @@ public async Task RunAsync_PretranslateAll()
 
         await env.RunBuildJobAsync(corpus1);
 
-        Assert.That(await env.GetPretranslateCountAsync(), Is.EqualTo(4));
+        Assert.That(await env.GetPretranslateCountAsync(), Is.EqualTo(2));
     }
 
     [Test]
@@ -87,7 +87,7 @@ public async Task RunAsync_PretranslateTextIds()
 
         await env.RunBuildJobAsync(corpus1);
 
-        Assert.That(await env.GetPretranslateCountAsync(), Is.EqualTo(4));
+        Assert.That(await env.GetPretranslateCountAsync(), Is.EqualTo(2));
     }
 
     [Test]
@@ -206,7 +206,11 @@ public async Task RunAsync_MixedSource_Paratext()
             Assert.That(trgCount, Is.EqualTo(1));
             Assert.That(termCount, Is.EqualTo(0));
         });
-        Assert.That(await env.GetPretranslateCountAsync(), Is.EqualTo(56));
+        Assert.That(
+            await env.GetPretranslateCountAsync(),
+            Is.EqualTo(11),
+            JsonSerializer.Serialize(await env.GetPretranslationsAsync())
+        );
     }
 
     [Test]
@@ -225,7 +229,7 @@ public async Task RunAsync_MixedSource_Text()
             Assert.That(trgCount, Is.EqualTo(1));
             Assert.That(termCount, Is.EqualTo(0));
         });
-        Assert.That(await env.GetPretranslateCountAsync(), Is.EqualTo(9));
+        Assert.That(await env.GetPretranslateCountAsync(), Is.EqualTo(3));
     }
 
     [Test]
@@ -488,10 +492,10 @@ await env.GetTargetExtractAsync(),
         });
         JsonArray? pretranslations = await env.GetPretranslationsAsync();
         Assert.That(pretranslations, Is.Not.Null);
-        Assert.That(pretranslations!.Count, Is.EqualTo(37), pretranslations.ToJsonString());
+        Assert.That(pretranslations!.Count, Is.EqualTo(3), pretranslations.ToJsonString());
         Assert.That(
             pretranslations[2]!["translation"]!.ToString(),
-            Is.EqualTo("Source one, chapter twelve, verse one.")
+            Is.EqualTo("Source one, chapter thirteen, verse one.")
         );
     }
 
diff --git a/src/ServiceToolkit/src/SIL.ServiceToolkit/Utils/ParallelCorpusPreprocessor.cs b/src/ServiceToolkit/src/SIL.ServiceToolkit/Utils/ParallelCorpusPreprocessor.cs
index e4a4dba8..0c728f0b 100644
--- a/src/ServiceToolkit/src/SIL.ServiceToolkit/Utils/ParallelCorpusPreprocessor.cs
+++ b/src/ServiceToolkit/src/SIL.ServiceToolkit/Utils/ParallelCorpusPreprocessor.cs
@@ -52,7 +52,7 @@ public void Preprocess(
                 {
                     ITextCorpus textCorpus = sc.TextCorpus;
                     if (sc.Corpus.TrainOnTextIds is not null)
-                        textCorpus = textCorpus.FilterTexts(sc.Corpus.TrainOnTextIds);
+                        return textCorpus = textCorpus.FilterTexts(sc.Corpus.TrainOnTextIds);
                     return textCorpus.Where(row =>
                         row.Ref is not ScriptureRef sr
                         || sc.Corpus.TrainOnChapters is null
@@ -66,7 +66,7 @@ row.Ref is not ScriptureRef sr
                     ITextCorpus textCorpus = sc.TextCorpus;
                     if (sc.Corpus.PretranslateTextIds is not null)
                     {
-                        return textCorpus.FilterTexts(
+                        return textCorpus = textCorpus.FilterTexts(
                             sc.Corpus.PretranslateTextIds.Except(sc.Corpus.TrainOnTextIds ?? new())
                         );
                     }
@@ -90,7 +90,7 @@ row.Ref is not ScriptureRef sr
                 {
                     ITextCorpus textCorpus = tc.TextCorpus;
                     if (tc.Corpus.TrainOnTextIds is not null)
-                        textCorpus = textCorpus.FilterTexts(tc.Corpus.TrainOnTextIds);
+                        return textCorpus = textCorpus.FilterTexts(tc.Corpus.TrainOnTextIds);
                     return textCorpus.Where(row =>
                         row.Ref is not ScriptureRef sr
                         || tc.Corpus.TrainOnChapters is null
@@ -309,9 +309,9 @@ private static IEnumerable<Row> AlignPretranslateCorpus(ITextCorpus[] srcCorpora
         foreach (
             ParallelTextRow? row in srcCorpora
                 .SelectMany(sc => trgCorpora.Select(tc => sc.AlignRows(tc, allSourceRows: true)))
-                .ZipMany(rows =>
-                    rows.Where(r => r.SourceSegment.Count > 0 && r.TargetSegment.Count == 0).FirstOrDefault()
-                )
+                .ZipMany(rows => rows.ToArray())
+                .Where(rows => rows.All(r => r.TargetSegment.Count == 0))
+                .Select(rows => rows.Where(r => r.SourceSegment.Count > 0).FirstOrDefault())
         )
         {
             if (row is null)