Trouble sending IR volume control using Arduino

Hello
I am currently trying to make a simplified IR remote control device for my McIntosh C2300 preamp.
I am using an arduino and the IRemote library.
The preamp uses the NEC protocol and, using IRrecvDump, I got the following codes for the keys I need:

Vol+
Decoded NEC: 53AA43BC (32 bits)

Vol-
Decoded NEC: 53AAC33C (32 bits)

Mute
Decoded NEC: 53AA639C (32 bits)

D/A
Decoded NEC: 53AAC936 (32 bits)

Tuner
Decoded NEC: 53AA49B6 (32 bits)

Power
Decoded NEC : 53AA03FC (32 bits)

Using the irsend.sendNEC() from the same library and an IR LED, I can send control the preamp to power on/off, mute and change inputs without any problem.
But I can't manage to change volume up or down, no matter if I send the command repeatedly and/or I use the repeat argument :

irsend.sendNEC(0x53AA43BC , 32, 3);

I also have the D100 DAC from the same brand, which has a volume control which works properly when provided the appropriate codes.
I also tried with an ESP32 with the no better results.
Any idea?
Thanks in advance.

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