diff --git a/sfm/idf_ascii_report.py b/sfm/idf_ascii_report.py
index ea26293..9775b42 100644
--- a/sfm/idf_ascii_report.py
+++ b/sfm/idf_ascii_report.py
@@ -65,9 +65,17 @@ def _normalize_key(raw: str) -> str:
 
 
 def _strip_unit_suffix(value: str) -> str:
-    """Return the numeric part of values like "0.2119 in/s" → "0.2119"."""
+    """Return the numeric part of values like "0.2119 in/s" → "0.2119".
+
+    Also strips Thor's below/above-threshold prefixes:
+      "<0.005 in/s"  → "0.005"   (below-noise-floor reading)
+      ">100 Hz"      → "100"     (above-measurement-range reading)
+    """
     parts = value.strip().split()
-    return parts[0] if parts else value.strip()
+    token = parts[0] if parts else value.strip()
+    if token.startswith("<") or token.startswith(">"):
+        token = token[1:]
+    return token
 
 
 def _parse_float(value: str) -> Optional[float]:
@@ -178,38 +186,54 @@ def parse_idf_report(text: Union[str, bytes]) -> Dict[str, Any]:
         except ValueError:
             pass
 
-    # Numeric scalars
-    for key in ("sample_rate",):
+    # Numeric scalars.  For every field we typify here, we MUST drop the
+    # raw string copy from `out` when parsing fails — Thor writes things
+    # like "<0.005 in/s" (below threshold) and "N/A" (not measured) that
+    # would otherwise linger in `out` as strings, sneak into SQLite REAL
+    # columns via permissive type affinity, and then crash the JS
+    # frontend on `.toFixed(...)`.
+    int_fields = ("sample_rate",)
+    for key in int_fields:
         v = raw.get(key)
-        if v is not None:
-            iv = _parse_int(v)
-            if iv is not None:
-                out[key] = iv
+        if v is None:
+            continue
+        iv = _parse_int(v)
+        if iv is not None:
+            out[key] = iv
+        else:
+            out.pop(key, None)
 
-    for key in ("tran_ppv", "vert_ppv", "long_ppv", "peak_vector_sum",
-                "tran_zc_freq", "vert_zc_freq", "long_zc_freq",
-                "tran_peak_acceleration", "vert_peak_acceleration",
-                "long_peak_acceleration",
-                "tran_peak_displacement", "vert_peak_displacement",
-                "long_peak_displacement",
-                "tran_time_of_peak", "vert_time_of_peak", "long_time_of_peak",
-                "mic_time_of_peak", "mic_zc_freq"):
+    float_fields = (
+        "tran_ppv", "vert_ppv", "long_ppv", "peak_vector_sum",
+        "tran_zc_freq", "vert_zc_freq", "long_zc_freq",
+        "tran_peak_acceleration", "vert_peak_acceleration",
+        "long_peak_acceleration",
+        "tran_peak_displacement", "vert_peak_displacement",
+        "long_peak_displacement",
+        "tran_time_of_peak", "vert_time_of_peak", "long_time_of_peak",
+        "mic_time_of_peak", "mic_zc_freq",
+    )
+    for key in float_fields:
         v = raw.get(key)
-        if v is not None:
-            fv = _parse_float(v)
-            if fv is not None:
-                out[key] = fv
+        if v is None:
+            continue
+        fv = _parse_float(v)
+        if fv is not None:
+            out[key] = fv
+        else:
+            out.pop(key, None)
 
     # Microphone — Thor reports MicPSPL (dB(L)) which is the closest
-    # analogue to BW's mic_ppv.  Stored as a float; units are in the
-    # original raw field (`mic_pspl` raw entry preserves "99.4 dB(L)").
+    # analogue to BW's mic_ppv.  The raw "99.4 dB(L)" string stays in
+    # `out` under the original `mic_pspl` key for display; the parsed
+    # float goes in `mic_ppv`.
     mic = raw.get("mic_pspl")
     if mic is not None:
         fv = _parse_float(mic)
         if fv is not None:
             out["mic_ppv"] = fv
 
-    # Record / pre-trigger duration
+    # Record / pre-trigger duration — same drop-on-failure discipline.
     rt = raw.get("record_time")
     if rt is not None:
         fv = _parse_float(rt)
diff --git a/sfm/sfm_webapp.html b/sfm/sfm_webapp.html
index 17474b4..7925c83 100644
--- a/sfm/sfm_webapp.html
+++ b/sfm/sfm_webapp.html
@@ -2285,13 +2285,16 @@ let sessLoaded   = false;
 const _unitSerials = new Set();
 
 function _ppvClass(v) {
-  if (v == null) return '';
-  if (v >= 2.0)  return 'ppv-high';
-  if (v >= 0.5)  return 'ppv-warn';
+  const n = (v == null) ? null : Number(v);
+  if (n == null || !isFinite(n)) return '';
+  if (n >= 2.0)  return 'ppv-high';
+  if (n >= 0.5)  return 'ppv-warn';
   return 'ppv-ok';
 }
 function _ppvFmt(v) {
-  return v != null ? v.toFixed(5) : '—';
+  if (v == null) return '—';
+  const n = typeof v === 'number' ? v : Number(v);
+  return isFinite(n) ? n.toFixed(5) : String(v);
 }
 function _fmtTs(ts) {
   if (!ts) return '—';
@@ -2386,7 +2389,11 @@ async function loadHistory() {
       <td class="${_ppvClass(ev.vert_ppv)}">${_ppvFmt(ev.vert_ppv)}</td>
       <td class="${_ppvClass(ev.long_ppv)}">${_ppvFmt(ev.long_ppv)}</td>
       <td class="${_ppvClass(pvs)}">${_ppvFmt(pvs)}</td>
-      <td class="td-dim">${ev.mic_ppv != null && ev.mic_ppv > 0 ? (20 * Math.log10(ev.mic_ppv / DBL_REF)).toFixed(1) + ' dBL' : '—'}</td>
+      <td class="td-dim">${(() => {
+        const m = ev.mic_ppv == null ? null : Number(ev.mic_ppv);
+        if (m == null || !isFinite(m) || m <= 0) return '—';
+        return (20 * Math.log10(m / DBL_REF)).toFixed(1) + ' dBL';
+      })()}</td>
       <td class="td-text">${ev.project ?? '—'}</td>
       <td class="td-text">${ev.client  ?? '—'}</td>
       <td class="td-dim">${ev.record_type ?? '—'}</td>