Hello Pikaboicu -
We are not aware of any issues on our end that would cause the gallery code to show as HTML in your listing descriptions as a result of editing an active listing. Please be sure that when you are making your edits you are using the description editor in Standard mode, unless you are proficient in editing the HTML. If you are editing elements of your own description and are only in Standard mode, there should be no means to bring the HTML of the gallery in to the description area of your listing.
If you continue to experience difficulty with this, please feel free to file a support case from under the Help tab of the site letting us know some listings where this has occurred and the exact steps you are using when making your edits and we will be happy to assist you further.