diff --git a/dam/source/cc/src/TpcTrimmedRange.hh b/dam/source/cc/src/TpcTrimmedRange.hh
index 462f3f6..2cae2f7 100644
--- a/dam/source/cc/src/TpcTrimmedRange.hh
+++ b/dam/source/cc/src/TpcTrimmedRange.hh
@@ -50,6 +50,8 @@
 
 #include "TpcStream-Impl.hh"
 #include "TpcCompressed-Impl.hh"
+#include <string>
+#include <iostream>
 
 namespace pdd    {
 namespace access {
@@ -299,6 +301,7 @@ inline uint32_t TpcTrimmedRange::Location::
                         int                               nTotFrames,
                         bool                                   begin)
 {
+   std::string myname = "TpcTrimmedRange::Location::locate: ";
    auto pktNum = pdd::access::TpcRangesIndices::getPacket (pktIdx);
    auto pktOff = pdd::access::TpcRangesIndices::getOffset (pktIdx);
    int   wfOff = nframesPerPkt * pktNum + pktOff;
@@ -311,20 +314,22 @@ inline uint32_t TpcTrimmedRange::Location::
    // the calculation, which depends on the data not
    // having certain pathologies, on the RCE fails.
    // ------------------------------------------------
-   if (wfOff > nTotFrames)
+   if (wfOff >= nTotFrames)
    {
       // ------------
       // Try guessing
       // ------------
-      wfOff = (timestamp - firstTimestamp) / 25;
+      //  
+      int wfOffNew = (timestamp - firstTimestamp) / 25;
 
       // ---------------------------------------------
       // Hopeless if this occurs before the timestamp
       // of the first WIB frame in the untrimmed data.
       // This likely indicates a complete corruption.
       // ---------------------------------------------
-      if (wfOff < 0) 
-      {
+      if ( wfOffNew < 0 || wfOffNew >= nTotFrames ) {
+         std::cout << myname << "WARNING: Skipping invalid frame index: " << wfOff << " --> "
+                   << wfOffNew << " >= " << nTotFrames << std::endl;
          m_wibOff = 0;
          m_pktNum = 0;
          m_pktOff = 0;
@@ -332,6 +337,10 @@ inline uint32_t TpcTrimmedRange::Location::
          return -1;
       }
 
+      std::cout << myname << "WARNING: Guess fixed invalid frame index: " << wfOff << " --> "
+                << wfOffNew << " / " << nTotFrames << std::endl;
+      wfOff = wfOffNew;
+
       pktNum = wfOff / nframesPerPkt;
       pktOff = wfOff % nframesPerPkt;
    }
@@ -359,7 +368,6 @@ inline uint32_t TpcTrimmedRange::Location::
       return 0;
    }
 
-
    // ----------------------------------------
    // Get the timestamp at the predicted point
    // ----------------------------------------