Losses in opening years

Suppose a person starts a trade and makes a trading loss in the 3rd tax year. They claim opening years relief and carry the loss back against the previous three tax years on a FIFO basis. Assume that, after this claim, there is still some total income remaining in those earlier years because the loss was not large enough to offset all of it. Now, in the 4th tax year, the person makes another trading loss. Can they make another opening years relief claim for the Year 4 loss and carry it back against the same previous three tax years Or is opening years relief available only once for the trade?