Problem exporting MXL files

Hi all,
First of all, I want to say that I have searched for this topic in the forum and I did not find anything, so here is my problem.
I am using MuseScore 4.2.1 in a Linux Mint machine (actually, I have been using MuseScore for many years). I usually create scores on it and sometimes I export them into XML format for another software. The problem is that when I create a multipart score with volta repeats, the resulting MXL file only contains the alternative information in the first part, not in the others. The measures are there, but they do not have the alternative volta information.
Apart from that, not all the score information is written in the XML file. The subtitle is one of the tags that are not exported.

Am I doing something wrong or is MuseScore always working like that?

Thanks in advance!

Lander