That's not an fix, Auldrick - it's barely a workaround. After the last update the trader refuses my stones also. I have some chests completely filled with stone from 1.12. Time for Mojang to make fixes to solve issues that reappear with every update - not suggest workaarounds that is sisyphuswork for us players.
Same here., with both cooked fish and stone.
Same here, on a Win 10 Pc.
Have tried your solution, Kenny. Sadly it didn't work on my old stone. 😞