Every election there are some issues or reports of problems at the polls by people on both sides. Some are legitimate, some are not. I don't know which category this one falls into.
But I do know the explanation from the McLennan County elections clerk seems reasonable. And I have absolutely no sympathy for anyone's vote not counting if they were too dumb to try and straight party vote and then try to vote again in the presidential election thereby wiping out their original selection. Serves you right for taking the lazy way out and voting straight party.
Keep in mind, I'm not talking about a seasoned citizen who doesn't know how to operate the electronic voting machine. That's a different case than what is described in the story below.