Like https://www.crumbsim.com/forum/bug-finding/wiring-bug-wire-hidden-in-board this bug ends up with a "broken" wire which is invisible, although the extra wire also seems to make the program allocate as much memory as possible (unlike in the other report). So far I've hit 30gb of RAM allocated before the viewport crashed (alongside my browser, where I was typing the first version of this report. RIP). So, I figure this is more of a bug than an intended limit. I've attached a design that is one wire below this limit (I haven't counted it, placing all of the wires to reproduce this was already painful enough). Placing another wire will cause the new wire to go invisible, and saving+loading the design with that one extra wire will cause all of the wires to disappear. Both situations will cause memory usage to go wild until the offending wire is removed or until the viewport crashes. In terms of a root cause, the only hint I noticed was that my original design (where I first ran into this problem) and the reproduction (which is attached) both had the viewport using around 4gb-ish of RAM used before things went wrong. I'm not sure if it is relevant, but I figure I might as well mention it.
Ok thank you! I shall take a look at this