Folks, please note that we are discussing here a very specific kind of “stuttering” which is indeed related to multiplayer: the behaviour is exactly as described by the OP, a completele “freeze” for like a quarter of a second, in regular intervals (each second or so).
So please do discuss general performance issues elsewhere. Again, this thread here is about a very specific performance problem related to multiplayer (as it seems anyway - “when more than N aircraft are nearby”).
We have experienced the same “interval stuttering” in the flight here:
The issue really impacted everyone who was “in the area with a high player densitiy”. We tried different aircraft as well (initially we all started with an X-Cub, but it happened with other types as well, including a “non-glass cockpit” aircraft, the Spitfire).
Both nVidia and AMD systems are affected.
The number of players (or distance) that it takes to reproduce this is not quite clear: stuttering disappeared once you moved away from “the flock” (like 20 nm), but as soon as you came closer (with “slew”) it started again.
At one point I counted like 15 nameplates around me, and it did not stutter (nor did it for others at that time - we exchanged our common experience via Discord), so the actual number of players that it takes to reproduce this is not quite clear (might be more in the vicinity of 20 players or so). But it is definitively related to the amount of players, and also possibly to the distance of each to one another.