So, i believe the biggest issue fundamental investors have is the information they rely on. Often, more often than you think, it's actually wrong, or sometimes it's just calculated in a way you didn't realise. I will use two cases to illustrate, from one investor class... the dividend investor.

I look at data every day, and dividend investors are looking for consistent and growing company dividend over time. Personally I want a dividend stock to be doing both. At least once a week, information about the stock I invest in is actually wrong. #arcc last week for eg on one site told me it paid a dividend of only 3 cents per share during 2 quarters of last year, totally wrong. Checking other sources quickly confirmed it to be totally wrong. Moral of the story... don't trust one source of data, always double and triple check. Reliable sources still get stuff wrong more often than you think. 

Second point, don't ever be lazy and rely on financial ratios calculated by others. Always do your own calculations. Why? Well they mite be wrong obviously, but they also mite be based on assumptions that are reasonable but maybe not applicable. 

Dividend return calculations for a company obviously include regular returns, and exclude special returns. Makes sense, most of the time. But there are some bdc's reits, etc that regularly pay quarterly special dividends. So while their dividend mite seem low at 6%, 8%, whatever... it might actually be 12%

Like and follow me please, friend me even better, I have just joined tiger because I'm ready to disobey myself regarding options trading. But I get it finally. Never buy anything you don't get. And I am here to discuss ideas, be part of a successful community of investors, adding my pennies worth