Status updates are only sent to players within a 40 block radius:

How to reproduce:

• Have player 1 stand more than 40 blocks away from the teleporter but still close enough for it to be loaded
• Activate teleporter with player 2
• Observe incorrect state for player 1 until another update is triggered

(Note: I haven't actually tried those steps. I just ran across it while adding compatibility for the teleporter to a different mod.)

I believe your suspicion is correct. I am going to also go through the few other remaining uses of sendToAllAround and see if they should be updated as well (it is likely they should)

Should be fixed by 63679fe (forgot to reference the issue from the commit)

Version 9.8.0 was just released and should sync to the twitch client within the next couple hours.