diff --git a/test/microwaveprop/workers/contact_weather_enqueue_worker_test.exs b/test/microwaveprop/workers/contact_weather_enqueue_worker_test.exs
index b3e674f8..6a89ef20 100644
--- a/test/microwaveprop/workers/contact_weather_enqueue_worker_test.exs
+++ b/test/microwaveprop/workers/contact_weather_enqueue_worker_test.exs
@@ -1,5 +1,9 @@
 defmodule Microwaveprop.Workers.ContactWeatherEnqueueWorkerTest do
-  use Microwaveprop.DataCase, async: true
+  # async: false — perform/1 runs inline Oban child jobs that upsert
+  # rows (iemre_observations, terrain_profiles) with a shared conflict
+  # target. Running concurrently with sibling DataCase tests produced
+  # intermittent "ShareLock deadlock_detected" failures in Postgres.
+  use Microwaveprop.DataCase, async: false
 
   alias Microwaveprop.Radio.Contact
   alias Microwaveprop.Terrain.ElevationClient
diff --git a/test/microwaveprop/workers/propagation_prune_worker_test.exs b/test/microwaveprop/workers/propagation_prune_worker_test.exs
index f856747d..98cb3e79 100644
--- a/test/microwaveprop/workers/propagation_prune_worker_test.exs
+++ b/test/microwaveprop/workers/propagation_prune_worker_test.exs
@@ -5,9 +5,13 @@ defmodule Microwaveprop.Workers.PropagationPruneWorkerTest do
   alias Microwaveprop.Workers.PropagationPruneWorker
 
   describe "perform/1" do
-    test "deletes ScoresFile binaries with valid_time older than 2 hours" do
+    test "deletes ScoresFile binaries with valid_time older than 3 hours" do
+      # `old` needs to sit strictly before the worker's computed cutoff
+      # (`now - 3h`). Both are truncated to the second when compared, so
+      # picking exactly -3h flakes whenever the test + worker wall-clock
+      # land in the same second. -3h - 1s gives unconditional ordering.
       now = DateTime.utc_now()
-      old = now |> DateTime.add(-3, :hour) |> DateTime.truncate(:second)
+      old = now |> DateTime.add(-3, :hour) |> DateTime.add(-1, :second) |> DateTime.truncate(:second)
       fresh = now |> DateTime.add(-30, :minute) |> DateTime.truncate(:second)
       future = now |> DateTime.add(6, :hour) |> DateTime.truncate(:second)
 
diff --git a/test/microwaveprop_web/live/map_live_test.exs b/test/microwaveprop_web/live/map_live_test.exs
index 63eecb09..a7c12273 100644
--- a/test/microwaveprop_web/live/map_live_test.exs
+++ b/test/microwaveprop_web/live/map_live_test.exs
@@ -120,6 +120,17 @@ defmodule MicrowavepropWeb.MapLiveTest do
   end
 
   describe "data timestamp indicator" do
+    setup do
+      # Earlier tests in the suite may have written score files into the
+      # shared `:propagation_scores_dir` and warmed the 5 s
+      # `list_valid_times` cache. Reset both so this test starts from the
+      # "no data" state its assertion describes.
+      scores_dir = Application.fetch_env!(:microwaveprop, :propagation_scores_dir)
+      _ = File.rm_rf(scores_dir)
+      :ets.match_delete(:microwaveprop_cache, {{Microwaveprop.Propagation.ScoresFile, :list_valid_times, :_, :_}, :_, :_})
+      :ok
+    end
+
     test "renders a 'Data from …' line on both mobile and desktop sidebars", %{conn: conn} do
       {:ok, _lv, html} = live(conn, ~p"/map")
       assert html =~ ~s(id="data-timestamp-mobile")