We are using FTB Revelations, running through Hamachi, with some mods added. We are using the latest version of ProjectRed (1.12.2-4.9.4.120).

It's an oddly specific bug, and seems to only work with only one of three players using the server. After a lot of testing with multiple mods and fixes, we determined that the cause was the rapid switching of lamps from on and off (I had a light cycling effect in my base, and he only DC'd upon coming close to it. Testing with single blocks and spamming a lever also caused him to DC.

Considering we share the base, it's kind of annoying that I can't use the coloured lamps in it. Only the block lamps cause the issues. Cage lamps, and other variants are fine after testing. So are lamps that remain placed, though placing them in larger amounts would disconnect him, just as switching their state.

The error he was getting is Internal Exception: java.io.IOException: An established connection was aborted by the software in your host machine.