The export of the questions does not assign them to the correct categories.

Steps to reproduce:

1. Create a new course
2. Go to the course question bank
3. On the categories tab, create two new categories "CatA" and "CatB"
4. Create a new question of type true/false, assign to category "CatA", question name "Q1" description "aaa"
5. Create a new question of type true/false, assign to category "CatB", question name "Q2" description "bbb"
6. Create a new question of type true/false, assign to category "CatA", question name "Q3" description "ccc"
7. On the Export tab, select "Moodle XML format" (or "Gift format"), select the category "Top for course" and Export question to file

Expected result:

Opening the exported file (in Moodle XML format or also in Gift format) I expected to see the questions Q1 and Q3 under the category "CatA" and the question Q2 under "CatB". If I delete the three questions and do the import, I expect the original situation as in Original categories.png screenshot.

Actual result:

Opening the exported file (in Moodle XML format or also in Gift format) I see the questions Q1 under the category "CatA" and the questions Q2 and Q3 under "CatB". If I delete the three questions and do the import (with both formats), I get the wrong situation as in Wrong categories.png screenshot.

I can reproduce the problem on version 3.5.4+, but on the version 3.6.2 (https://demo.moodle.net/) it works correctly.