New Customized Object (AL Extension) sometimes cant be found

Hi All,

I have customized new object in AL Extension

page 80001 "New General Setup"
UsageCategory = Tasks;
ApplicationArea = All;
DeleteAllowed = false;
InsertAllowed = false;
PageType = Card;
SourceTable = "NewGeneral Setup";

everything is ok.
user can see and access.
but sometimes it couldn't be found.
once I restarted the service, then user can find New General Setup 
my question : how did it happen?
I cant find what is the root cause this page couldnt be found.
Please advise.