I get the same error message as David does.
Regardless, it should be "Patterson's film" or "the Patterson film".
The word "real" is also misused here. The film is obviously "real" to the extent that it exists. The question is whether Patterson and Gimlin actually filmed a "bigfoot" in the wild, or whether they perpetrated a hoax, as did the people that created the infamous Loch Ness Monster photograph.
As to the grammatical question, "if" should be in quotation marks. Consider this, and imagine that we are all between 16 and 19 years old:
Yes, you can borrow my car next week, but only if your sister goes to the dance with me this Friday. And that's a big "if". She'd better do a couple of slow dances with me, and kiss me goodnight when I drive her home.
The "qualified if" of your original quote means that the author is in serious doubt about the authenticity of what is seen on the film. His statement is poorly worded and punctuated, if you have presented it accurately to us. And that's a big "if".
I'll make a deal with you, though. If monkeys fly out of my butt today, I'll send you a check for $1000 (USD). Consider this a very very big qualified "if".
Good luck with that.