My HC still catches multiple hits, too. I was hoping that the last update was going to fix that. Like you, I also return them.I still have some HITs catch twice in Hit Catcher, but I manually return the second one after completing the first one.
Hit Tracker, I'm frequently having to select today's date in the date range once a day as Hit Tracker can't seem to track today's date reliably.
I suppose a hit could have been worked twice and shown up once in hit tracker if the hits were done at the midnight time frame when hit tracker goes thru a day change (so one hit could show up on one day's activity, that hit done again could show up in the next day's activity).
This is the first time in my 4 years of turking that I've ever receive a rejection for being accused of completing a hit twice. So this is the first time I am using HT to further research this issue, even though I already know that I never completed two of these hits. I've sent a few emails asking them for their proof, but they have yet to respond. Based on my experience, fair and honest requesters usually reply, and shady ones do not...