This is a known issue with multiplayer and the window out-of-focus implementation of certain browsers.
I'd be interested to know more about this, if anyone has some details about it. I don't destroy or recreate any synced objects while my game is playing (except when peers connect/leave). So having objects disappear and reappear (with their non-synced values reset), and sometimes not recreated at all, is a bit concerning.
I feel like it is related to the latency simulation.. but I haven't tested it with real-world high latency yet to find out.
I tested it locally WITHOUT latency simulation, with nw.js minimized and it was alright.
When I tested with simulation, I tried testing with simulation values of 0.000001 and minimized, and the latency would begin climbing up to 900s when minimized (objects disappearing while this happens), and then when unminimized the latency of the peer would fall back down below 50.
So I think there is something within the simulation itself that is causing problems..
again, i haven't tested with real-world high latency- but I have with low latency, locally, and when minimized the latency doesn't begin to climb(since the latency isn't simulated).
Also keep in mind, that if the synced objects don't have their data changed much, they timeout quicker.