The world it has been happening on was a survival server on hard with 2 other people who are playing in the same room over a lan connection we will be playing and for a long time over 4 hours without exiting server the first time it happened we were tunneling at lava level going to our spawn location which was very far from where we decided to settle and when we tried exiting the mine a wall had respawned like 10 blocks thick behind us so re dug it out and continued onward and it happened again at the same exact spot on our way back we decided to save and quit a reload and when came back we had lost maybe 2 or three hours worth of exploring and my friends spawned in some random cave and died immediately because they had no idea where they were when this happened we were actually playing the previous update and when we quit and came back the game updated so we thought it may have been fixed but when we played we made all our progress back and quit it was all there so we thought it was resolved until last night i was playing by myself and my friends came over and signed on we played for 7 hours about and we putting down another rail system trying to make a villager farm and when im testing out the rails going the other way some of the sand we removed was back so we figured it was probably happening again save and quit relaunch world to find we literally had no work saved from the time my friends started playing all the same items and same locations as when they signed on the roof we put on our building gone we are really curious wether this is maybe due to the world being played while the udate came out or if its because were on lan because i cant seem to find anybody else experiencing this problem