After Installing K-Lite I hear audio only from 1 speaker

This has happened before, but I didn't trace it back to K-Lite then. Last time I tried reinstalling/upgrading/downgrading my sound card drivers and it didn't work, so I formatted my PC. After that everything was OK, this time, I after installing K-Lite, everything was fine, but after restarting my PC, the audio is again heard only from the left speaker. This time I'm sure that the only action that could result in this was installing K-Lite, though, like the other time, I didn't try uninstalling K-Lite yet.

Also there's one significant difference from my current problem and the one before formatting. I hear both left and right on my headphones now, but the other time headphones also worked only on the left side.

Any suggestions?

Disconnect your speakers and reconnect them. Play something and fiddle with the wire of the silent speaker. I suspect it is a broken wire.

Codecs certainly don't cause this. Driver problem is unlikely too given the randomness of the problem.

Well, the last time, as I said, a simple format fixed the problem. Also, I forgot to mention that I'm on a laptop, so I can't disconnect the speakers.

Codec Tweak Tool > Audio Output > select Stereo
Then click on the Windows Sound Settings button. Select Speakers and click on Configure. Verify that Windows is set to stereo as well. Then click on Properties button. At the levels tab you can find volume level settings. Click on Balance button to verify that both Left and Right speaker are equal.

That made it even worse... Now my headphones also play only the left.

upd: Headphones are OK now. But speakers are still left-only

Exactly which changes broke and fixed the headphones? Maybe your sound driver has its own settings as well that you also need to adjust?

Not sure, I changes several things. Tried to simulate the same situation again, but it didn't work. Driver's own settings don't do anything either.