When network traffic is unsettled, it is possible for triggers to be deferred. This can happen mid execution of any trigger when activating a custom trigger. Deferred custom triggers then will execute out of order. This breaks the assumption on triggers and can happen differently on each client, unsyncing them even when things appear to be setup correctly. The most noticeable form of this is when buffering events that call into custom triggers. When a new player joins, these buffered triggers tend to execute everything on the trigger itself and defer all custom triggers, causing them to execute on a later frame. This makes it impossible to buffer triggers properly if you never know if the trigger will execute the same frame or on later frames.
Example world: wrld_37443b7e-2bc5-4f1b-82e1-7c81f384b601
While this world does not show deferred events in the log, it shows some triggers executing out of order. There are a large number of boxes with text. Each box does the same thing. They have an OnInteract AlwaysBufferOne that first calls into a local custom trigger to set the text to 1 and then outside of the custom trigger sets the text to 2. Clicking them in the world will show 2 for everyone. Clicking all the boxes and then having someone else join will then show some with 1 instead of 2, proving the custom trigger ran out of order. It is also possible for the entire buffer event to fail but that is a different canny post.