The bridge should not make the invite-only room public

[seekstar]

Our room has been made private to prevent spam. However, when I bridge to telegram, the bridge makes the room public.

!tg bridge xxx
!tg continue
Telegram bridge bot made the room public to whoever knows the link.
// Puppets enter the room by themselves without invitation
!tg config view
{}

What's weird is that the bridge acts normally in another testing room:

searchstar (@searchstar:matrix.org) made the room invite only.
Telegram bridge bot joined the room
...
!tg continue
Telegram bridge bot invited Matrix Bridge (Telegram)
Matrix Bridge (Telegram) joined the room
Telegram bridge bot invited search star (Telegram)
search star (Telegram) joined the room
!tg config view
{}

The bridge bot is the moderator of two Matrix rooms and is a user with default permissions in the two corresponding telegram rooms. It does not make any sense that the bridge bot acts differently in the two rooms.

P.S. The two rooms use the same bot: @telegrambot:tchncs.de whose !tg version returns mautrix-telegram 0.12.1. Although it is not the latest version, it seems that there is no related commit since the version. So I guess the latest version also has the problem.

EDIT: I recently find that even after making the room private again, a new user entering the telegram room will still make the corresponding puppet enter the Matrix room by itself without invitation. Following the first example:

!tg bridge xxx
!tg continue
Telegram bridge bot made the room public to whoever knows the link.
// Puppets enter the room by themselves without invitation
You made the room invite only.
// UPDATE: The room became public sometime without notifying my Matrix client (Both Element and FluffyChat).
// User A joined the telegram room
Puppet A joined the room. //Without invitation!!!

UPDATE: I'm astonished to learn that the room became public sometime, even though my Element client shows that it's private.