Cross platform server constantly crashed due to full RAM

I have a server for switch and pc players, the server has 4GB RAM with no plug in or MODs at all. We only 1-2 players online at the same time, but no matter how many players online, the RAM just went up to full in a sec and then crashed the server.

We've upgraded the plan to 2GB RAM to now 4GB, but the problem still exists. We tried to reload the back-up from a couple hours ago, then we could be able to play for a while, but all of a sudden, the RAM just went up for no reason, even we aren't building anything.

We cannot play anymore. Please help, thanks. 

 

here are some log attached