Hi everyone I'll try and be as detailed as I can

I'm currently having an issue with a Bell VIP5662w box, the box works with a Bluetooth remote however I've reset the box and removed the Bluetooth remote from the equation, and the box only works through IR now.

The strange issue that I'm having is;

the none of IR blasters off of the the mrf260 are able to control the the box, I've moved the position over the entire front face of the box, I have tried different blasters, I've used both variable and fixed outputs of the MRF, I've changed the blaster strength on the MRF through the whole range available.

All other devices inside of this cabinet are working correctly.

the only way I am able to get it to work currently is using the mrx 890 with the cabinet doors open AND I have to point the remote AWAY from the box i.e. at the wall on the opposite side of the room, pointing the remote directly at the box results in nothing working. I haven't come across this problem before usually with bell remotes I've just had to mess around with placement but it's usually worked out otherwise am I missing something?

Full disclosure: I have no experience with this unit.

Could this be a signal strength issue? If so, attenuate the signal received by the VIP5662w with some tape over it's IR receiver. Experiment with partial occlusion, pinholes, or tape color if the tape is not completely opaque.

Another area to explore is the number of repeats baked into each command.

Which code set are you using?
For some cable boxes, there are multi code sets depending on if you are using IR direct from the remote or using IR from the RF base station.
This could be your problem.

Could you please clarify which codes you are referring to? The RF base stations and remote controls used by various cable boxes employ different infrared (IR) codes.