diff --git a/src/hwapi.cpp b/src/hwapi.cpp
index 035f73e..9fa3633 100644
--- a/src/hwapi.cpp
+++ b/src/hwapi.cpp
@@ -2640,12 +2640,23 @@ void hwapi::bl_openBinary(void) const
 void hwapi::bl_sendDataBlock(uint8_t length, uint8_t *buffer) const
 {
     // send 64 byte from bin file
-    uint8_t LL=length, sendBuf[80], sendLen;
+    // gh, 09/02/2024: extend sendBuf. Buffer sometimes too small, sendLen=81
+    uint8_t LL=length, sendBuf[80+32], sendLen;
     if (LL>64) LL=64;
 
-    tslib_strclr(sendBuf,0,80);
+    memset(sendBuf, 0, sizeof(sendBuf));
     sendLen=dcBL_prepareDC_BLcmd(0x22, LL, buffer, sendBuf);   // pack into protocol frame
+
+    // qCritical() << "(" __func__ << ":" << __LINE__ << ") sendLen=" << sendLen
+    //             << ":" << QByteArray((const char *)sendBuf, sendLen);
+
     sendWRcmd_setSendBlock160(sendLen, sendBuf);                  // send 140 bytes
+
+    // if (sendLen > 80) {
+    //    qCritical() << "(" << __func__ << ":" << __LINE__ << ")"
+    //                << QByteArray((const char *)&sendBuf[80], 32).toHex(':');
+    // }
+
     delay(100);
 }