lag in timer

My upload speed is 120Mbps, download speed is 250Mbps, ping is below 5ms. I am not using any extension. My browser is updated. I am using chrome. I play rapid, Any other time control rather than 30 minutes is just unplayable. I premove everything or make move within 2 second still loose on time. for example, I have 60 seconds, and it is king and queen endgame i premove everything and suddenly my clock has less than 10 seconds, 5 seconds and i loose game on time. It looks like my clock runs even when my opponent is thinking to make his move. I know it is not my internet problem nor my device problem as i have tried from multiple devices.  I also tried app, and it is worse. The ping bar is good sometimes and sometimes it says reconnecting but mostly it shows excellent connection.
Things i did to solve it which did not work. 
1. Clear all cookies and ensure browser has no cache or extension enabled.
2. Used only 1 tab for chess.com
3. Contacted my isp and they made sure it has no problem, and they are right other game has 0 internet problem.
4. Tried using vpn.

If there is any solution, please mention it.

i got the solution. lichess$ better. i am switiching to lichess

It is due to chesscom server overload!!!