Webserver on ESP8266 hangs when mobile device connects

So when I connect to my local webpage from a desktop browser on as many different computers as I want, I am able to load my page. However, once I load it from my smartphone all the pages on my desktop become non-responsive and only load when I refresh my mobile page. Closing the page on my mobile has no influence. When desktop clients connect it ends with client disconnected. However when I connect from my smartphone, it ends also with client disconnect followed with New client and then hangs??
While I expect it to keep looping over loop(). I am not sure why this happens to solely my chrome smartphone browser.

Code :

#include <Arduino.h>
#include <ESP8266WiFi.h>
#include <Time.h>

typedef struct timekeepers_t timekeepers;

struct timekeepers_t{
  unsigned long currtime=100000;
  unsigned long prevtime=0;
};

// Replace with your network credentials
const char* ssid     = "name";
const char* password = "passw";

// Set web server port number to 80
WiFiServer server(80);

// Variable to store the HTTP request
String header;

void setup() {
Serial.begin(115200);
Serial.print("Connecting to ");
  Serial.println(ssid);
  WiFi.begin(ssid,password);
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }
  // Print local IP address and start web server
  Serial.println("");
  Serial.println("WiFi connected.");
  Serial.println("IP address: ");
  Serial.println(WiFi.localIP());
  server.begin();
}

void loop() {
WiFiClient client = server.available();
 if (client) {                             // If a new client connects,
    Serial.println("New Client.");          // print a message out in the serial port
    String currentLine = "";                // make a String to hold incoming data from the client
    while (client.connected()||client.available()) {            // loop while the client's connected
      if (client.available()) {             // if there's bytes to read from the client,
        char c = client.read();             // read a byte, then
        Serial.write(c);                    // print it out the serial monitor
        header += c;
        if (c == '\n') {                    // if the byte is a newline character
          // if the current line is blank, you got two newline characters in a row.
          // that's the end of the client HTTP request, so send a response:
          if (currentLine.length() == 0) {
            // HTTP headers always start with a response code (e.g. HTTP/1.1 200 OK)
            // and a content-type so the client knows what's coming, then a blank line:
            client.println("HTTP/1.1 200 OK");
            client.println("Content-type:text/html");
            client.println("Connection: close");
            client.println();
            
            client.println("<!DOCTYPE html><html>");
            client.println("<head><meta name=\"viewport\" content=\"width=device-width, initial-scale=1\">");     
            //client.println("<html><head><meta http-equiv="Content-Type" content="text/html;charset=utf-8">");
            client.println("<link rel=\"icon\" href=\"data:,\">");
            // CSS to style the on/off buttons 
            // Feel free to change the background-color and font-size attributes to fit your preferences
            client.println("<style>html { font-family: Helvetica; display: inline-block; margin: 0px auto; text-align: center;}");
            client.println(".button { background-color: #4CAF50; border: none; color: white; padding: 16px 40px;"); //open button
            client.println("text-decoration: none; font-size: 30px; margin: 2px; cursor: pointer;}");
            // Web Page Heading
            client.println("<body><h1>Garage door</h1>");
            
            // Display current state, and ON/OFF buttons for GPIO 26  
            // If the state is off, it displays the ON button       
            client.println("</body></html>");
            
            // The HTTP response ends with another blank line
            client.println();
            // Break out of the while loop
            break;
          } else { // if you got a newline, then clear currentLine
            currentLine = "";
          }
        } else if (c != '\r') {  // if you got anything else but a carriage return character,
          currentLine += c;      // add it to the end of the currentLine
        }
      }
    }
    // Clear the header variable
    header = "";
    // Close the connection
    //client.print('A');
    client.stop();
    Serial.println("Client disconnected.");
    Serial.println("");

try to use my StreamLib's ChunkedPrint, to sent the html in larger chunks and to let the browser know the end of data.

I read the description of your library but I am not too sure if it applies here.

I should stress the issue is that mobile devices bugs out the program see my serial monitor:

WiFi connected.
IP address:
SNIPPEDAWAY
New Client.
GET / HTTP/1.1
Host: SNIPPEDAWAY
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:67.0) Gecko/20100101 Firefox/67.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8
Accept-Language: en-US,en;q=0.5
Accept-Encoding: gzip, deflate
Connection: keep-alive
Upgrade-Insecure-Requests: 1
Cache-Control: max-age=0

Client disconnected.

New Client.
GET / HTTP/1.1
Host: SNIPPEDAWAY
Connection: keep-alive
Cache-Control: max-age=0
Upgrade-Insecure-Requests: 1
User-Agent: Mozilla/5.0 (Linux; Android 9; LYA-L29) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/72.0.3626.121 Mobile Safari/537.36
DNT: 1
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,image/apng,*/*;q=0.8
Accept-Encoding: gzip, deflate
Accept-Language: en-NL,en;q=0.9,nl-NL;q=0.8,nl;q=0.7,en-US;q=0.6

Client disconnected.

New Client.

I can connect as many desktop client browsers as I want, only mobile devices bugs it out and hangs at new client, while normally after client disconnect it starts looping again whereas it stays inside the while loop when a mobile devices connects.

Try using ESPwebserver instead.