Use of crontab can be confusing especially for adminstrators with different user crontabs to manage.
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What we do is each user has a directory cron in their home directory (except root which is in another location known to all of the administrators).
To create the crontab in the first place create a file called "ct". To load it 'crontab ct'.
When you want to modify it first do a 'crontab -1 > ct2'. Then a 'diff ct ct2' to ensure that you got the one you wanted. If there are no differences edit ct and then load it 'crontab ct'.
If you find differences, resolve them and proceed accordingly. This helps avoid stepping on the wrong crontab by accident as well as checking that someone else has not modified the file using some other procedure - a hacker?
Of course the directory "cron" should be restricted to only the user (700).