"The content type is in use" message

Hi,

I have created a bunch of content types and then decided that I don't needed them. I'm trying to delete the content types but I keep receiving a message "The content type is in use":

This is what I tried so far:

- I removed all custom lists, libraries, etc. that might have used the content types.

- I have removed all custom columns from the content types.

- I removed all custom columns from the web site.

- I emptied both Recycle Bins (web-level and site-collection level)

- I run the code from MSDN that deletes content types or shows usage if there is any. In my case the code detects that there is no usage and tries to delete content types which generates the same error message ("The content type is in use")

https://msdn.microsoft.com/en-us/library/office/ms453791%28v=office.14%29.aspx?f=255&MSPPError=-2147217396

Is there anything else I should try in order to get rid of unwanted content types?

Thanks,

Leszek

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