Convert a Pattern of Bad Data to Null

[DataSundowner]

Hi everyone. I have a column contains a bunch of bad entries such as "000000", "1111", "00000000000", "2222222" etc. Basically, it's a string with repetitive digits, and length of the string is not specific. How can I efficiently convert this kind of pattern to nulls in Power Query? Thank you! 

[DataSundowner]

@amitchandak Thank you for your reply. I found out the following post and it met my needs. 
https://stackoverflow.com/questions/57775536/power-query-how-to-delete-duplicate-characters-from-a-s...

[amitchandak]

@DataSundowner , does correct values have some pattern?

Can you share sample data and sample output in table format?