Random chunks resetting

My server has many long nether highways connecting our bases, but sometimes when the server crashes (which seems to happen alot in 1.14.1 Pre-Release 1) some to many chunks in the nether just get "reset", deleting everything in them.

(Due to an error, i cant upload images, so here is a link to a screenshot of a reset chunk and here a screenshot of the server console)

Till now, i have not seen this "chunk reset" happen in the overworld nor the End yet

The warning messages, the frequent crashes and the chunk resets only started once we updated to 1.14.2 Pre-Release 1, it was fine in 1.14.1