What you need to know:

If (improperly) tested by moving a single cable from the left output to the right output, the left channel will seem louder than the right. This is completely normal.

This is an improper test because, the Left channel includes both left and right channels summed in mono when you use a single cable. You will see it is clearly labeled “L/Mono”. This means: in a situation where you are using this instrument with a mono sound system, a single cable connected to this jack will include a phase coherent sum of both Left and Right signal

The Right channel, when a cable is plugged in (assumes you are using both channels) only includes the right channel information. Using a single cable to the right channel is never correct.

Here’s a test you can try
Recall the Init Normal (FM-X) Performance — a Single, Mono Sine wave delivered to both Left/Right channels equally.
Use two standard TS cables, one to each output (as I’m sure you know to do)... connect to your Audio Interface.
Setup a Stereo Audio Track in Cubase or your favorite DAW
Using the audio meters of your DAW, you should get an even reading in each channel. (see attached screenshot of MODX in Cubase 10)

If you’re receiving more in one channel than the other, switching leads should switch the problem.
Contact your authorized Service Center or call your regional Yamaha Customer Service desk.

In the attached screenshot - you see the signal derived from the Init Normal (FM-X) Performance, All Effects Bypassed....
Bypass your Effects by tapping the "FX" icon top center of the MODX screen.

Hey thank you for your response!!
So i tried the experiment that you suggested and the result was that both channel were reading the same! So its no the output of the MODX that is the problem. so thats awesome.
Although the experiment worked, im still not understanding how to record the actual sound from the MODX. When i play the CFX Concert performance, while listening with headphones connected to the MODX phones jack, everything sounds fine, and even both left and right.
But when i listen from my interface, with the audio coming from the left/right outputs on the MODX into my interface with a line signal, im still experiencing less volume on one side of the headphones. I can also see the difference in signal from each channel through the console software from my interface. Again, the interface is fine, the headphones are as well..nothing wrong there. So im left thinking its the cables..which again, are like you said, (2) TS cables.. and yes the cables are the same length.
So how do i get that same stereo presence and evenness in channels from the MODX's outputs to my daw to record?

So how do i get that same stereo presence and evenness in channels from the MODX's outputs to my daw to record?

”Stop thinking with your eyes!” I remember hearing that from my audio engineering instructor... they can help, but your ears are king in this domain. Here’s what I mean by this...

The CFX Concert is a stereo instrument... this means it was sampled using two microphones creating a stereo result. You will notice it also is programmed so that the lower you play on the scale the more signal that arrives on the left channel. Forgive the next question (some people take it the wrong way) but, have you ever played an acoustic grand piano? Observe the amount of signal that arrives at each each ear as you play a scale from low to high... your left ear hears more of the piano, not only because it’s on your left, but the lid, the mass of the lower strings, and your position as player makes the piano slightly louder in your left ear.

Play the stereo acoustic pianos in the MODX, the lowest note clearly is on your left (assuming you have your sound system setup properly) and as you play up the scale more signal arrives at the right.

Yes, the pianos are positioned to emulate the player’s position (as opposed to the audience position). The benefit of a Stereo sampled instrument is clearly the experience of sitting *at* the piano, over sitting in the audience. Sitting “at” the piano you get more of a left/right panorama, the farther away you get from the piano, the less you are aware of this stereo image, as the room becomes more involved. Using Reverb, for example, will place the listener farther away from the instrument, less cognizant of that left-to-right image.

There are several instrument sounds in the MODX that are sampled in stereo, to give a more realistic experience when performing them.