Mojave spell check keeps flagging correct words and tries to change them to grammatically incorrect words So this has been driving me crazy - it feels like I have a grammar troll living in my computer.  MacOS's spell checker keeps flagging words as misspelled that aren't. I notice it mostly in Mail, because that's what I use most.  However it's also happened in Messages and other Apple apps.  It does not happen in MS Word.  Usually it's trying to get me to use another similar word that is grammatically incorrect.  I've attached some screenshots as well.  

Hardware is a 2017 iMac 5K running 10.14.1 (non-beta), and I don't remember seeing this before Mojave. I don't have any other languages installed other than U.S. English, am located in the U.S., and don't have any settings that are anything other than what a regular, American English speaking person would have. I also don't have any other spell-check programs installed that I know of.  This is only a work computer with the basics installed.  Has anyone else come across this, or have any idea what it could be?

For example, the following sentences have popped up as issues (quotes are added by me here, they were not in the original text):

"The second claim is what's left, and is what you should respond to here." It flags "here" and tries to change it to "hear".  

"We should go somewhere in town that's closer to downtown". It flags "to" and tries to change it to "too".

"I just contacted your office."  It flags "your" and tries to change it to "you're". 

"You had the proper address and were going to bring it to her."  It flags "were" and tries to change it to "we're".

Does anyone have an idea of what this could be? I would suspect some rogue app doing this, but I am careful with what I install, and only have trusted apps on the machine.
According to this apple support discussion many are experiencing the same issue.

One way to get rid of is to install Grammarly for Mac and turn off apple spell check.