Almost always one of three reasons, and rarely a fault.
The FPX transaction fee. If RM100 becomes roughly RM99.30 the instant you deposit, that is the payment provider's fee, deducted before investment. It is not a loss.
Currency movement. The underlying holding is USD-denominated. If the ringgit strengthens, your MYR value falls even though the investment itself is fine. It reverses when the ringgit weakens.
Normal day-to-day movement. The target rate is an annual figure, not a daily guarantee. Individual days can be slightly negative even when the yearly trend is positive.
The target rate is a projection. It is not a floor.