Game not rendering

I have been playing Starbound multiplayer with my Nephews and have run into a problem. Sometimes when they load into my server they can only see the blocks and the ui. He cannot see, his own player character, my character, any mobs, and torches, any plants or trees, or any crafting stations.

Note: sometimes the game is playable for hours with no issues.

Our setup:
His computer- Connecting to server using IP (not steam-link)
Mac OS 10.9.5
2.66 Ghz Core 2 Duo
8GB RAM

Mine (running dedicated server) - I'm connecting to Localhost, however connecting to IP causes me no problems either
macOS 10.12.3
2.5 Ghz Core i7
16 GB RAM

When My brother (my nephew's father) plays with me from his higher power gaming tower we have never had any connection or rendering issues. IE: not a network or internet issue causing data loss.
My wife also connects to the server through a local IP and has never had problems with it either (doesn't seem to be the server).

Things we have tried:
Restart client computer
Restart server
Restart Steam
Restart Starbound
Verify Starbound via steam file verification (no problems)
disable steam's in-game overlay
disable multiplayer via steam friends
Turn graphics settings lower. (we've gone to lowest available resolution with no change).

Oddly, when this particular computer has this issue, it affects both single and multiplayer. However it doesn't happen to him when playing Single Player, it always starts from multiplayer. The only solution we've found at this point is to wait and try again another day (this sucks because we don't have tons of time to play anyway).

Any other ideas out there?

 

on the computers this is a problem, does it happen in single player?

if it does, this command may b helpful:

 

yes he has

 

The problem never starts in single player. When it does start happening, it does affect single player too. I'll try having him toggle visible layers next time it happens.

 

Toggling layers didn't have any affect on this issue.

Any other ideas out there?
Anybody getting the same issue?