diff --git a/src/ifcviewer/ViewportCore.cpp b/src/ifcviewer/ViewportCore.cpp
index f1f1c048e4..32cdf80268 100644
--- a/src/ifcviewer/ViewportCore.cpp
+++ b/src/ifcviewer/ViewportCore.cpp
@@ -7870,8 +7870,20 @@ void ViewportCore::render() {
              || camera_distance_  != prev_camera_distance_
              || camera_yaw_deg_   != prev_camera_yaw_deg_
              || camera_pitch_deg_ != prev_camera_pitch_deg_);
+        if (camera_moved) {
+            motion_cull_latched_ = true;
+            motion_hold_timer_.start();
+        } else if (motion_cull_latched_
+                   && motion_hold_timer_.elapsed() >= kMotionHoldMs) {
+            motion_cull_latched_ = false;
+        }
+        // While the latch holds with the camera still, keep frames coming so
+        // the expiry actually happens and the fine-threshold re-cull runs —
+        // the loop is on demand, and a fully-resident scene would otherwise
+        // stay coarsely culled until the next input.
+        if (motion_cull_latched_ && !camera_moved) host_->requestFrame();
         const bool use_motion_threshold =
-            camera_moved && motion_min_pixel_radius_ > min_pixel_radius_;
+            motion_cull_latched_ && motion_min_pixel_radius_ > min_pixel_radius_;
         const float effective_min_px =
             use_motion_threshold ? motion_min_pixel_radius_ : min_pixel_radius_;
         last_cull_was_motion_ = use_motion_threshold;
diff --git a/src/ifcviewer/ViewportCore.h b/src/ifcviewer/ViewportCore.h
index 7bf2846256..86d86a3be1 100644
--- a/src/ifcviewer/ViewportCore.h
+++ b/src/ifcviewer/ViewportCore.h
@@ -1632,6 +1632,19 @@ private:
     double last_cull_compute_ms_          = 0.0;
     double last_cull_upload_ms_           = 0.0;
     double last_stream_ms_                = 0.0;
+    // Motion-cull latch. The coarse motion threshold used to follow the
+    // per-frame "did the camera move" test directly, which flip-flops
+    // during a slow low-fps drag: coalesced mouse events leave frames
+    // where the camera happens not to change, so the cull alternated
+    // between the 3 px and 15 px thresholds — most of the scene vanishing
+    // and reappearing every few frames, with a full visible-set re-upload
+    // at each flip. The latch holds the coarse threshold until the camera
+    // has been still for kMotionHoldMs, so a drag degrades once at its
+    // start and restores once, shortly after it ends.
+    static constexpr int kMotionHoldMs = 250;
+    bool      motion_cull_latched_ = false;
+    Stopwatch motion_hold_timer_;
+
     // True when the cull just used motion_min_pixel_radius_ — render()
     // schedules one more frame so the camera-now-stopped state recomputes
     // the cull at the still threshold and previously dropped sub-pixel