diff --git a/cores/esp8266/Updater.cpp b/cores/esp8266/Updater.cpp
index 28830fba52..7ad21300a9 100644
--- a/cores/esp8266/Updater.cpp
+++ b/cores/esp8266/Updater.cpp
@@ -38,14 +38,14 @@ void UpdaterClass::_reset() {
 bool UpdaterClass::begin(size_t size, int command) {
   if(_size > 0){
 #ifdef DEBUG_UPDATER
-    DEBUG_UPDATER.println("already running");
+    DEBUG_UPDATER.println("[begin] already running");
 #endif
     return false;
   }
 
 #ifdef DEBUG_UPDATER
   if (command == U_SPIFFS) {
-    DEBUG_UPDATER.println("Update SPIFFS.");
+    DEBUG_UPDATER.println("[begin] Update SPIFFS.");
   }
 #endif
 
@@ -73,6 +73,12 @@ bool UpdaterClass::begin(size_t size, int command) {
     //address where we will start writing the update
     updateStartAddress = updateEndAddress - roundedSize;
 
+#ifdef DEBUG_UPDATER
+        DEBUG_UPDATER.printf("[begin] roundedSize:       0x%08X (%d)\n", roundedSize, roundedSize);
+        DEBUG_UPDATER.printf("[begin] updateEndAddress:  0x%08X (%d)\n", updateEndAddress, updateEndAddress);
+        DEBUG_UPDATER.printf("[begin] currentSketchSize: 0x%08X (%d)\n", currentSketchSize, currentSketchSize);
+#endif
+
     //make sure that the size of both sketches is less than the total space (updateEndAddress)
     if(updateStartAddress < currentSketchSize) {
       _error = UPDATE_ERROR_SPACE;
@@ -88,7 +94,7 @@ bool UpdaterClass::begin(size_t size, int command) {
   else {
     // unknown command
 #ifdef DEBUG_UPDATER
-    DEBUG_UPDATER.println("Unknown update command.");
+    DEBUG_UPDATER.println("[begin] Unknown update command.");
 #endif
     return false;
   }
@@ -100,6 +106,12 @@ bool UpdaterClass::begin(size_t size, int command) {
   _buffer = new uint8_t[FLASH_SECTOR_SIZE];
   _command = command;
 
+#ifdef DEBUG_UPDATER
+  DEBUG_UPDATER.printf("[begin] _startAddress:     0x%08X (%d)\n", _startAddress, _startAddress);
+  DEBUG_UPDATER.printf("[begin] _currentAddress:   0x%08X (%d)\n", _currentAddress, _currentAddress);
+  DEBUG_UPDATER.printf("[begin] _size:             0x%08X (%d)\n", _size, _size);
+#endif
+
   _md5.begin();
   return true;
 }
@@ -168,9 +180,14 @@ bool UpdaterClass::end(bool evenIfRemaining){
 }
 
 bool UpdaterClass::_writeBuffer(){
+
+  yield();
+  bool result = ESP.flashEraseSector(_currentAddress/FLASH_SECTOR_SIZE);
+  yield();
+  if (result) {
+      result = ESP.flashWrite(_currentAddress, (uint32_t*) _buffer, _bufferLen);
+  }
   yield();
-  bool result = ESP.flashEraseSector(_currentAddress/FLASH_SECTOR_SIZE) &&
-                ESP.flashWrite(_currentAddress, (uint32_t*) _buffer, _bufferLen);
 
   if (!result) {
     _error = UPDATE_ERROR_WRITE;
@@ -217,29 +234,32 @@ size_t UpdaterClass::write(uint8_t *data, size_t len) {
 }
 
 size_t UpdaterClass::writeStream(Stream &data) {
-  size_t written = 0;
-  size_t toRead = 0;
-  if(hasError() || !isRunning())
-    return 0;
-
-  while(remaining()) {
-    toRead = FLASH_SECTOR_SIZE - _bufferLen;
-    toRead = data.readBytes(_buffer + _bufferLen, toRead);
-    if(toRead == 0){ //Timeout
-      _error = UPDATE_ERROR_STREAM;
-      _currentAddress = (_startAddress + _size);
+    size_t written = 0;
+    size_t toRead = 0;
+    if(hasError() || !isRunning())
+        return 0;
+
+    while(remaining()) {
+        toRead = data.readBytes(_buffer + _bufferLen,  (FLASH_SECTOR_SIZE - _bufferLen));
+        if(toRead == 0) { //Timeout
+            delay(100);
+            toRead = data.readBytes(_buffer + _bufferLen, (FLASH_SECTOR_SIZE - _bufferLen));
+            if(toRead == 0) { //Timeout
+                _error = UPDATE_ERROR_STREAM;
+                _currentAddress = (_startAddress + _size);
 #ifdef DEBUG_UPDATER
-      printError(DEBUG_UPDATER);
+                printError(DEBUG_UPDATER);
 #endif
-      return written;
+            }
+            return written;
+        }
+        _bufferLen += toRead;
+        if((_bufferLen == remaining() || _bufferLen == FLASH_SECTOR_SIZE) && !_writeBuffer())
+            return written;
+        written += toRead;
+        yield();
     }
-    _bufferLen += toRead;
-    if((_bufferLen == remaining() || _bufferLen == FLASH_SECTOR_SIZE) && !_writeBuffer())
-      return written;
-    written += toRead;
-    yield();
-  }
-  return written;
+    return written;
 }
 
 void UpdaterClass::printError(Stream &out){
diff --git a/cores/esp8266/WString.cpp b/cores/esp8266/WString.cpp
index f92344b84e..4ba4b1f9f2 100644
--- a/cores/esp8266/WString.cpp
+++ b/cores/esp8266/WString.cpp
@@ -121,6 +121,7 @@ ICACHE_FLASH_ATTR String::~String() {
     if(buffer) {
         free(buffer);
     }
+    init();
 }
 
 // /*********************************************/
@@ -136,8 +137,7 @@ inline void String::init(void) {
 void ICACHE_FLASH_ATTR String::invalidate(void) {
     if(buffer)
         free(buffer);
-    buffer = NULL;
-    capacity = len = 0;
+    init();
 }
 
 unsigned char ICACHE_FLASH_ATTR String::reserve(unsigned int size) {
diff --git a/cores/esp8266/WString.h b/cores/esp8266/WString.h
index 4c502bfe54..3f216cee4d 100644
--- a/cores/esp8266/WString.h
+++ b/cores/esp8266/WString.h
@@ -76,7 +76,11 @@ class String {
         // invalid string (i.e., "if (s)" will be true afterwards)
         unsigned char reserve(unsigned int size);
         inline unsigned int length(void) const {
-            return len;
+            if(buffer) {
+                return len;
+            } else {
+                return 0;
+            }
         }
 
         // creates a copy of the assigned value.  if the value is null or