Thermostat issues

Been a while since I've posted, but nobody here in the US has an answer.
When I got my car I was always impressed at how cool it ran. As soon as winter arrived, it turned out it wasn't warming up at all. I disassembled it and found that the previous owner had removed the thermostat. I installed a thermostat, and it worked about six months. Then it started sticking. A few taps from a hammer, and the thermostat would open. I blew the hose from the water tube to the thermostat housing. I ordered Gaskets and replaced the thermostat again. I had already ordered the hose because I saw it swelling.
About six months later, here I am with the same problem. The thermostat is sticking again, and a few taps from a hammer will open it. Both times I used a Stant brand thermostat. Both times I replaced the gaskets and made sure I was running 50/50 coolant.
Whatever is happening, it happened at least once to the previous owner, and twice to me. Replacing the thermostat doesn't fix it. Cooling system has been dumped three or four times by me. There's no oil in the coolant or coolant in the oil. No bubbles when running. Does anyone have any further ideas? Is there a different thermostat I should be running? Could some other component that might cause the thermostat to stick?
GVX/DMB1300

Thanks again,
Buck

Bad quality parts maybe?

I think that thermostat fit from golf mk 2 petrol,not shure..that is just bad thermostat

But three in a row from Stant? That's statistically unlikely. I can replace it again, but odds are it will do the same thing again.

Never heard for that brand,maybe its just bad,made for yugos to last 6 monts and than die yugo and thermostat to just buy new one 😁

Maybe you could try this one
https://www.autozone.com/cooling-heating-and-climate-control/thermostat/duralast-thermostat/710504_140457_1632

There was a trick with those kind of thermostat's that you should drill a small hole in the top cover but I don't know why or where exactly. Some people on forum probably know that better than me and if that even makes sense. I don't know why but I remember that I've saw someone writing about that trick and how good it worked.