Unexpected ETA value

[Ericlyclyclyc]

This.

And this.

I submit three different fullrender task to the queue. And the task for world started first. The next is world_nether, but after a little while( i did nothing), it returns to world and...see image 2.

It's quite a small problem but now i can't see the ETA.
There is no error reports in my console.