welp its been doing it since I've been playing..except it won't do that on my IPAD only on my phone.
I play exclusively on my iPad. Won't even install it on my phone 'cause I wanna stay employed

Anywho, when FIRST started playing, it would come back and say that the word(s) you played was/were inappropriate, but didn't identify the word. As TJ pointed out, if you lay down multiple words, you don't know WHICH word (s) are wrong.
Then there was an upgrade. With the upgrade, it tells you WHICH word(s) you've misspelled.