Weird FPS cap issue

[Redon]

I've been considering giving Disco another try, but after reinstalling it, I've run into a strange problem where playing online seems to cap my frame rate to exactly 100 fps in a seemingly arbitrary way, which I'll try to explain in more detail below. First, I should mention that I use a 144 Hz monitor, but I run it at 120 Hz with LightBoost. I've been using the Nvidia control panel to toggle vsync on or off, and Fraps to benchmark fps.

• At 120 Hz with vsync, the game initially runs at a constant 120 fps as long as I don't connect to the server. I can play like this offline for as long as I want and not have any problems. As soon as I connect to the server though, the fps cap begins alternating between 120 fps and (exactly!) 100 fps at seemingly random intervals. Here's what that looks like over the course of about 20 minutes.
  
• At 144 Hz with vsync, the same thing happens, except that it is alternating between 144 fps and 100 fps.
  
• With Vsync disabled, the game initially runs at about 180 fps while offline, but as soon as I connect to the server, the frame rate is permanently capped at 100 fps.
  
• In all three cases, the described behavior persists even after disconnecting from the server and loading an offline save. Only restarting the game seems to fix it.
  
• This behavior occurs regardless of whether I use the -noframelimit option in the launcher.
  

Unfortunately, the frame rate feels very choppy when this 100 fps limit is active, much more than you might expect based on the numbers. The difference is jarring and makes it hard to enjoy the game. I've reinstalled Freelancer and the Discovery mod from scratch at least twice, to no avail. I've not experienced such problems with any other games. The fact that this only happens once I connect to the server seems especially odd to me. I'd love to understand what's going on here.