If they are pure nonsense I don't know how grammarly can correct them. Like how grammarly is correct this content:
There was a time in his life when her rudeness would have set him over the edge. He would have raised his voice and demanded to speak to the manager. That was no longer the case. He barely reacted at all, letting the rudeness melt away without saying a word back to her. He had been around long enough to know where rudeness came from and how unhappy the person must be to act in that way. All he could do was feel pity and be happy that he didn't feel the way she did to lash out like that.
or this
It was a concerning development that he couldn't get out of his mind. He'd had many friends throughout his early years and had fond memories of playing with them, but he couldn't understand how it had all stopped. There was some point as he grew up that he played with each of his friends for the very last time, and he had no idea that it would be the last.
It gotta make some sense and have some relevancy to begin with.