Szymon Adamus
I just did a run through of your workflow as close as I could come to source media, project settings, and export settings. I could not reproduce the loss of the right channel (or any channels) after export.
A just in case question...if you take your export into the Premiere Elements project, open the Audio Meters (Window Menu/Audio Meters) and place back the file with only the left channel displaying in the Timeline audio track, do you see activity in just the left vertical bar of the Audio Meter?
Also, in your details of Codecs installed, I saw mention of "Xvid MPEG-4 video Codec". Xvid is bad news for Premiere Elements (any version). Is Xvid involved in this project in any way?
We will watch for further developments. If you do the uninstall/reinstall of the program, please consider the sequence...
uninstall
ccleaner run through to get rid of leftovers from incomplete installs and/or uninstalls
CCleaner - PC Optimization and Cleaning - Free Download
reinstall with antivirus and firewall turned Off
Premiere Elements 7 does not have a Help Menu/Deactivate in the opened program. But if you see a request to deactivate during uninstall, then please use that option so that activation of the product will be needed in the reinstall.
ATR