You can be pretty confident that the IR transmission works. No need to swap IR LEDs.
Please try with another device to convince yourself.
So it is probably some quirk in the device. Is it this thing:
[Link: uk.humaxdigital.com] ? The webpages says
* The Humax Aura remote control supports both infrared and Bluetooth connectivity.
* Your remote is already paired with your recorder via infrared. During the initial set up process, we will guide you to pair your remote via Bluetooth.
* The remote LED will flash Red when paired via infrared and Green when paired via Bluetooth.
so there appears to be an error potential.
If using the original remote, can it control the thing without eye contact?