Rss Feed works on and off, help needed please

I have noticed that my rss feed on the page sometimes work and sometimes not, I am not sure but it seems that when some characters appears on the post then the feed does not appear well,
this was the error once when clicked on my rss feed on my blog:
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An invalid character was found in text content. Error processing resource ‘https://www.mywebsite.com/blog/feed/’. …

Find in a Library: The work-at-home mom’s guide to home business : stay …
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I think the invalid character might be those numbers after text, here is the actual text of that part on the above:

Find in a Library: The work-at-home mom’s guide to home business : stay

so the wp add some numbers, and possibley this cause problem,

anyone can help ?

thanks