Robotdyn uno r3 serial communication with esp, not working

I use a Robotdyn, uno+wifi r3 atmega328p+esp8266.It was functioning fine. I had got the esp and the uno to communicate, and anything I wanted logs for, I got them over the web server, both for uno and esp. Strangely, the serial communication with esp has stopped. So, I changed the setting to check esp's serial communication separately. What ever I tried to put to esp using serial monitor does not seem to reach it and vice versa. I tired the same exercise with uno, and it seems to work perfect.

I've verified the switch connectivity in the board, it does not seem to have a problem. Most of the posts online seems to explain the basics of serial connectivity based on the table provided for serial communication by robotdyn.

I do not have an idea, how to debug this further. Any leads would be very helpful.

Did you use voltage level translation hardware between the Uno and the ESP pins? Oh, wait, sorry, those would be on board that device...

But in moving the board jumpers around, it's possible you blew something...

Did you ever do anything to alter the ESP firmware? Like uploading a sketch to it?

Yes, I have my custom code both in uno and in esp.

basic protocol is;

get mtr speed on esp web server.
send "MtrSpeed:0-255" on serial to arduino
Arduino responds when speed is set to pin.
esp webserver responds.

I got a new device, to verify, and even there, I face the same issue.

When I have sw 5 and 6 on, and reset the device, my serial.println stuff comes to serial monitor, but what I give as input in serial monitor does not reach esp.

Post it. Use code tags.

In uno

void serialEvent() {
  static int cmd=0;
  static String lstr="";
  static String subCmd="";
  while(Serial.available() > 0) {
    char inChar=(char)Serial.read();
    if (cmdIsSet) {
      if ((inChar == '\n') || (inChar == '\r')) {
        // cmd is set and subCmd is populated fully.
      } else
        subCmd+=inChar;
    } else
      lstr+=inChar;
      
    if (inChar == ':') {
      Serial.print("Received from esp - ");
      if (lstr.equalsIgnoreCase("MtrSpeed:"))
        cmd=CMD_MtrSpeed;
    if(cmd != 0)
    cmdIsSet=true;
    } else if ((inChar == '\n') || (inChar == '\r')) {
    if(cmdIsSet) {
    switch(cmd) {
    case CMD_MtrSpeed:
    {
      int sped=subCmd.toInt();
      analogWrite(mtrPin, sped);
      String resp=" MtrSpeed:"+subCmd;
      Serial.println(resp);
      loopSpeedSent=0;
      lstr="";
      subCmd="";
      cmdIsSet=0;
      cmd=0;
      break;
    }
  }
}

In esp

void findConfInSerial() {
  static String subCmd="";
  static int cmd=0;
  bool cmdIsSet=false;
  static String lstr="";
  while(Serial.available() > 0) {
    char inChar=(char)Serial.read();
  if (cmdIsSet) {
    if ((inChar == '\n') || (inChar == '\r')) {
      Log+=lstr+" : "+subCmd;
    } else
      subCmd+=inChar;
  if (inChar == ':') {
    Serial.print(" Received colon ");
    Serial.println(lstr);
      if (lstr.equalsIgnoreCase( "MtrSpeed:")) {
       String spd=Serial.readStringUntil('\n');
       respondSpeedReq(spd);
    }
}

The snippet is stripped out of my original code, since this is the section I am trying to unit test. Other wise the combined code runs to few hundreds of lines.

Please, no snippet. Post the few hundred lines.