Large difference in ping in game vs out of game

Hi Conanites,

I have a question on cause of large ping in game but very low ping direct to server.

I play on a private modded server. I have a 15ms to 20ms steady ping if I ping the IP-Address and the server select in CE shows the same. But once in game the ping in the game is 150ms to 750ms and it takes many seconds for contents of personal inventory and chests to load.

What would be the causes of the in-game lag?

Unsure of the server spec but when there are more players on the ping gets worse/higher and the load times for items in containers increases with number of players online yet pinging the IP-Address of the server maintains a steady 20ms ping.