The cause of the matter is that I found out the pistons can push blocks out of the island , Then I accidentally found that I could not go back to Personal Dimension （like Image 1）
When I blocked the portals on both sides , I was trapped in the portals and be teleported again and again🤣

Ah, pistons. So many Minecraft bugs caused by pistons.

A fix for pistons pushing blocks outside of the build space might be hard. But at least this bug requires the player to actively shoot themselves in the foot.

You can get out of this infinite loop with the portalCooldown parameter in the server config. Set it to something higher so that you have time to enter spectator mode and fly out. Then use the /setblock command to turn the blocks that you pushed to air.

The 'reach-around' block placing feature of Quark can also cause this.