While I don’t typically actively trade Lumber Futures, I do track their prices. I recently was confused by a change to the symbol at Barchart.com from LS to LB.
I found this very helpful article about the change in the contract. Much more changed than just the symbol, the dimensions and other specifics about the contract changed as well.
The size of the contract is much smaller, from about a train car of lumber to a truck of lumber. Also the prices don’t really match up so this should be added as a new item and not spliced back into the old Lumber contract. This is a fairly substantial change.