When you take the teleporter after defeating Leandra, it should lead to the First Garden, which is a new area in the End of Time, not back to where Zixzax is.

There was a similar issue fixed in the PC version, which will be in the next console patch, but the destination was different (start of Whispers of the Void, rather than the previous section of the End of Time). If this has the same cause, it may also be fixed in the next update.

Did you try loading a save before defeating Leandra and choosing different options at the end (not performing the soul forge, leaving the sisters behind, etc).

Please email supportdos@larian.com, with a description of the problem and the report.zip file (or a Dropbox or Google drive link, etc) generated by the D:OS EE Analysis Tool (for Windows).
Extract the zip file somewhere and run the AnalysisTool.exe. When that loads, browse to the install folder (if it is not automatically detected), optionally run the tests first, and then generate a report (it will be saved in the same location as the Analysis Tool).

The report will contain system and game information, as well as your saved games. To reduce the file size, you can delete most of the saves from the zip, just leaving one before using the teleporter, and maybe one with Leandra almost defeated, if available.

Console saves can be sent, as well, but they would need to be transferred to a USB flash drive first, and a third party tool is required for drives formatted for Xbox One (see here).