Deja Vu Fell Off The Map

So I was doing the quest deja vu and I'm at that part where you have to stop Aster from dying from the crane and explosion and cosmic event. So Aster dies from the cosmic event, and I'm teleported back to Aster's house with Old Man Martyn which is "vanished in time" according to him. But the game lags for a few seconds and I walk forward several blocks while this is happening. When the game stops lagging I'm outside of the house but there's nothing below me, so I suddenly start falling and falling and falling and slowly take damage until I die. Once I die I spawned back in Ragni, so I ran back to Time Valley, but when I try talking to Aster, it says something like "Aster is frozen in time, unable to move or speak" HELP ME. DON'T KNOW HOW TO COMPLETE QUEST.

 

Bring him his shovel again or try to enter the house

 

thanks. Your tip worked.