I get the message "Inventory Full" when I try to buy Unstable Plasma, despite the fact that my inventory and my ship has plenty of slots free. Happens everywhere, in space stations and trading posts. Other products are ok to buy.

Is this a single issue or are other items concerned too? It's rather annoying, the Unstable Plasma is needed to reload the Grenades in the multitool.

Works for me in 2.09.3. I can't remeber running into this with anything I ever bought at Trade Terminals.

But I still sometimes get the dreaded 'Inventory Full' bug when interacting with Storage Containers (plus I can't switch to the Exosuits Cargo inventory when interacting with a Storage Container anymore since Beyond ... that's really inconvenient)

I have solved this matter. It's because I have tried to buy 59 Unstable Plasma not knowing that they will only stack by x5 in a slot. I didn't have enough cargo room so the game prevented me to buy them which is normal.
Therfore I was wrong: it's not a bug :)

Oh, tell me ... I really, really miss how Atlas Rises did show, if you were buying over available inventory space, instead of just telling you 'No free slots in inventory' like NEXT and Beyond do now.