While pasting the Un protected Cells became Protected an locked

Hello,

I made A excel work book called (Customer Daily balance) to be used by my Employees(users), this sheet is calculating the recent balance of each customer in $ By interring a specific data In A Proper Cells ( by pasting from another Excel Sheet which called the (source), and for your Info this (Source) is not protected/ locked at all

According to (Customer Daily balance) , I made those cells which the users Pasting the data in opened < unlocked/unhidden> ( unprotected)

And the columns which include the Formulas and the confidential equation are Protected and locked
Selcet Column> formate cells> protection> Locked, hidden
Protected sheet > allow the users to use all the option> mark all to insert row, delete row,formate cell,formate row ,,,,ETC)


the problem that the users encountered is while pasting the data into the cells, which are unprotected) ,the whole Column become protected and locked !!!!!! I don't know how and why
and they couldn't use the cells in the second row until I make the sheet unprotected and select the column >formate cells> unlocked>unhidden to be unprotected again to make sure that the column of interring data return Back to be unlocked and then I protect the sheet again


do you think they must use Paste special or There is something else wrong in my sheet
I will be very grateful,if you Provide me a solution for that problem