diff --git a/.github/workflows/reusable-build-test-config.yml b/.github/workflows/reusable-build-test-config.yml
index 66f46709cd..83ece81919 100644
--- a/.github/workflows/reusable-build-test-config.yml
+++ b/.github/workflows/reusable-build-test-config.yml
@@ -230,6 +230,8 @@ jobs:
           BUILD_NPROC: ${{ steps.nproc.outputs.nproc }}
         run: |
           set -o pipefail
+          # Coverage builds are slower due to instrumentation; use fewer parallel jobs to avoid flakiness
+          [ "$COVERAGE_ENABLED" = "true" ] && BUILD_NPROC=$(( BUILD_NPROC - 2 ))
           ./xrpld --unittest --unittest-jobs "${BUILD_NPROC}" 2>&1 | tee unittest.log
 
       - name: Show test failure summary
diff --git a/src/test/app/LedgerReplay_test.cpp b/src/test/app/LedgerReplay_test.cpp
index 5568a90d03..4428e82ea9 100644
--- a/src/test/app/LedgerReplay_test.cpp
+++ b/src/test/app/LedgerReplay_test.cpp
@@ -1128,9 +1128,27 @@ struct LedgerReplayer_test : public beast::unit_test::suite
         BEAST_EXPECT(net.client.waitAndCheckStatus(
             finalHash, totalReplay, TaskStatus::Completed, TaskStatus::Completed, deltaStatuses));
 
-        // sweep
-        net.client.replayer.sweep();
-        BEAST_EXPECT(net.client.countsAsExpected(0, 0, 0));
+        // sweep() cleans up skipLists_ and deltas_ by removing entries whose
+        // weak_ptr can no longer be locked. Those weak_ptrs expire only when the
+        // last shared_ptr holder releases the sub-task. The sole owner is the
+        // LedgerReplayTask, but a JobQueue worker thread may still hold a
+        // temporary shared_ptr to a sub-task (from wptr.lock()) while executing
+        // the timer job that drove the task to completion. If sweep() runs before
+        // that thread unwinds, the weak_ptr is still lockable and the map entry
+        // is not removed. We retry until the worker thread finishes.
+        auto waitForSweep = [&net]() {
+            for (auto numAttempts = 0; numAttempts < 20; ++numAttempts)
+            {
+                net.client.replayer.sweep();
+                if (net.client.countsAsExpected(0, 0, 0))
+                {
+                    return true;
+                }
+                std::this_thread::sleep_for(std::chrono::milliseconds(100));
+            }
+            return false;
+        };
+        BEAST_EXPECT(waitForSweep());
     }
 
     void
diff --git a/src/test/rpc/Subscribe_test.cpp b/src/test/rpc/Subscribe_test.cpp
index 414bceefd7..9a24980d49 100644
--- a/src/test/rpc/Subscribe_test.cpp
+++ b/src/test/rpc/Subscribe_test.cpp
@@ -802,13 +802,17 @@ public:
          * return {true, true} if received numReplies replies and also
          * received a tx with the account_history_tx_first == true
          */
-        auto getTxHash = [](WSClient& wsc, IdxHashVec& v, int numReplies) -> std::pair<bool, bool> {
+        auto getTxHash = [](WSClient& wsc,
+                            IdxHashVec& v,
+                            int numReplies,
+                            std::chrono::milliseconds timeout =
+                                std::chrono::milliseconds{5000}) -> std::pair<bool, bool> {
             bool first_flag = false;
 
             for (int i = 0; i < numReplies; ++i)
             {
                 std::uint32_t idx{0};
-                auto reply = wsc.getMsg(100ms);
+                auto reply = wsc.getMsg(timeout);
                 if (reply)
                 {
                     auto r = *reply;
@@ -982,7 +986,7 @@ public:
             BEAST_EXPECT(goodSubRPC(jv));
 
             sendPayments(env, env.master, alice, 1, 1);
-            r = getTxHash(*wscTxHistory, vec, 1);
+            r = getTxHash(*wscTxHistory, vec, 1, 10ms);
             BEAST_EXPECT(!r.first);
         }
         {
@@ -1001,7 +1005,7 @@ public:
                 return;
             IdxHashVec genesisFullHistoryVec;
             BEAST_EXPECT(env.syncClose());
-            if (!BEAST_EXPECT(!getTxHash(*wscTxHistory, genesisFullHistoryVec, 1).first))
+            if (!BEAST_EXPECT(!getTxHash(*wscTxHistory, genesisFullHistoryVec, 1, 10ms).first))
                 return;
 
             /*
@@ -1161,7 +1165,7 @@ public:
             {
                 // take out existing txns from the stream
                 IdxHashVec tempVec;
-                getTxHash(*ws, tempVec, 100);
+                getTxHash(*ws, tempVec, 100, 1000ms);
             }
 
             auto count = mixedPayments();
@@ -1195,7 +1199,7 @@ public:
             {
                 // take out existing txns from the stream
                 IdxHashVec tempVec;
-                getTxHash(*wscLong, tempVec, 100);
+                getTxHash(*wscLong, tempVec, 100, 1000ms);
             }
 
             // repeat the payments many rounds