sound leaking from one right to left channel

I want to completely separate 2 mono tracks and play one only to the left channel and the other only to the right. I found out that even if its very low the Right channel is leaking to the left, and vice versa. For example if a play where the arrow is in the attached photo (where there is only Right channel audio), and i fully open only the Left speaker, i can here a little of the R channel. Its low, but i would like to completely separate them (until now, i just pan one channel all to R and the other all to Right, as shown in the image).

In the digital domain the left & right are completely separate.

In analog electronics there is usually SOME stereo “crosstalk” (leakage from one channel to the other).
That can happen during recording (where it will exist in the digital file) or it can happen at playback time.

Most stereo equipment has a crosstalk spec of -60dB or better so it’s rarely a problem. (Your soundcard MAY be worse than that.) With vinyl records you can only get about -20dB but that’s still low enough that you can’t hear it under normal listening conditions.

Modern professional recording is usually done in multi-track with each instrument recorded separately and in mono. Then the tracks are panned left-to-right during mixing. If the engineer pans something 100% left or 100% right, there will be no crosstalk in the digital recording. Most stereo recordings don’t have anything panned 100%, but some do.

But sometimes a multitrack recording is made with multiple microphones and the whole band playing in the same room at the same time. In that case there will be "leakage’ or “bleed” into the other mics and when the tracks are panned they won’t be perfect.

Windows audio (playback) enhancements* can introduce crosstalk between left & right …
Here’s how to turn them off …

[ * there can be a second layer of audio enhancements provided by the computer manufacturer,
sometimes called MaxxAudio ].

It’s also sometimes used as a “headphone enhancement”, presumably to simulate listening to speakers in a room (or any sound in a room) where all sounds reach both ears. In this case it’s usually called “crossfeed”.

I haven’t record anything myself. I want to play totally different track in each (left and right) channel.

I tried disabling Windows audio (playback) enhancement but still the same. Also, i found out Ableton doesn’t do that.
Is any other Audacity preference to completely disable left and right bleeding?

IMO you can exclude Audacity as the cause of bleeding.
MaxxAudio can cause crossover bleed on playback
MaxxAudio's MaxxSpace causes bleed.png
(MaxxAudio can be on by default when the computer is new).