Can't buy a DLC I already have?

I wanted to get a DLC for cheap GS since they are half price right now, but I already have them, and steam won’t let me buy any again. Is this just steam or it’s working as intended?

Steam will not let you buy the same dlc if you already own it. If you want to purchase it again, you will need to do it via the Gaijin Store for Star Conflict.

And if the synergy % would stack too…

You can only purchase a DLC twice, if you buy it 1x on stem and 1x on the gaijin store.

So, when buying the second one via gaijin instead of steam, I get the DLC? Taking into account that I loose everything inside that account, except the gold?

ok, it works, just confirmed it - you get all the gold, but no additional benefits (like the ships you already have etc.)