Cell Replicates Another Cell For No Apparent Reason

[Philb1]

I've found a cell that replicates another cell on the same sheet. If any number or text is entered, its replicated as text, but if I enter a formula in the cell, the cell works normally. There's no conditional formatting, no links, no macro, no nothing that I can see, yet it happens. Clear all hasn't worked, Google hasn't come up with an answer.
Any ideas please?
Thanks