Did you use the latest version?
Do you all use tablets to play the map?
Does your server has necessary computing power?
Did you change anything in the config?
For instance the max amount of alive enemies or the particle effect for treb sling. Try lowering the max amount of alive enemies to 30 and see if it still fails.

引用自 Elko：

Did you use the latest version?
Do you all use tablets to play the map?
Does your server has necessary computing power?
Did you change anything in the config?
For instance the max amount of alive enemies or the particle effect for treb sling. Try lowering the max amount of alive enemies to 30 and see if it still fails.

What do you mean about using all tablets?
Server is rocking 2 6 core Xeon CPU's
No I haven't changed the config for Horde
Yeah it's the latest version.

Set 'maxAliveEnemies' to 35 and see if it still lags.

So I did a stress test running wave 101 with server and client on my medium rig laptop (i7 4710MQ + gtx 860M + Win10).
Was running smoothly, ping was around 40.

The issue is probably your graphic settings. In other game modes there are never so many characters at once. So make sure you turn the character detail mode down and the ragdolls.
For the test I had some other settings turned down too but these 2 should be the main ones.

引用自 Elko：

So I did a stress test running wave 101 with server and client on my medium rig laptop (i7 4710MQ + gtx 860M + Win10).
Was running smoothly, ping was around 40.

The issue is probably your graphic settings. In other game modes there are never so many characters at once. So make sure you turn the character detail mode down and the ragdolls.
For the test I had some other settings turned down too but these 2 should be the main ones.

No because everyone in the server would lag.

Or each of your friends need to adjust settings.
Otherwise you can run a bandwith check.