Black dots after command fill or worldedit

Hello, minecraft builders, i found bug in the 1.14.1. we have server with my friends and i am angry after filling the mountain with air i need flat on buildings, and *after fill there are big black dots and small black dots.* Small black dots can be deleted, you place block and remove block and black dot is nt there. I don t found any answers on this bug, so i am writing here... Thanks for reading and solving the bug, THX. PS: down is screenshot, ia m czech sry for my english.