The post, I was looking for. Unfortunately, there isn't any resolution yet :(
: After looking the code and searching for any solution I found out that a new field: SortOrder has to be added to be_Pages table. There is one SQL Query, which I found in the Setup scripts and I ran it:
ALTER TABLE dbo.be_Pages ADD
SortOrder int NOT NULL CONSTRAINT DF_be_Pages_SortOrder DEFAULT 0
CREATE NONCLUSTERED INDEX IX_be_Pages ON dbo.be_Pages
) WITH( STATISTICS_NORECOMPUTE = OFF, IGNORE_DUP_KEY = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY]
Run this and next time you try to add new page, hit the Settings button in the bottom of the page and fill all the fields there, especially the Sort Order one.
It worked for me, I hope it will work for you too