since 1.15 items and blocks that are dropped or mined become invisible, but can be picked up if near. reloading data packs or refreshing chunks doesn't work, only way to fix it is leaving the server and logging back in. i also tried using optifine but it didn't help, since the update im playing vanilla and still doesn't work. other players on the realm don't have any problems. im adding a youtube link because the file size is too big to attach. 

https://www.youtube.com/watch?v=gh25kFisoVA