Stews coagulating after freezing
Experiment and see if flour acts the same as cornstarch. I find that cornstarch tends to "set up" in such a way that food remains a gelatinous blob after reheating. It does this after being refrigerated too, so I don't think it has to do with you actually freezing it: just cooling it down.

I think flour works a little better to reheat which is why I tend to try to use that for things which I know I will want to reheat and eat again later.

Lastly, do make sure you get it piping hot when reheating as this will help to smooth it out and will also melt and gelatin that comes from the meat.