If the fx impact is bigger than the loss why not sell the stock and buy it cheaper?

So I've seen a couple of times my stocks showing gain while they're still down mostly to the fx impact.

If this difference is bigger than the taxes payed why shouldn't I just sell the stocks and buy them at their current cheaper price?

Really curious about if this would be a good idea and what's wrong with it, cause it seems to good to be true tbh.

Thanks for your help!