In an extracted backup directory there are .xml files that relate to things like files, resources, etc.
Examples:
-rw-r--r--. 1 root root 793635 May 29 17:50 questions.xml
At the top of above file:
<?xml version="1.0" encoding="UTF-8"?>
<question_categories>
<question_category id="1">
<name>top</name>
<contextid>126</contextid>
<contextlevel>50</contextlevel>
<contextinstanceid>12</contextinstanceid>
<info></info>
<infoformat>0</infoformat>
<stamp>site+180907081818+PqQpnN</stamp>
<parent>0</parent>
<sortorder>0</sortorder>
<questions>
</questions>
</question_category>
Then, under the above which appears to define categories ...
<question_category id="2">
<name>Default for Skill Check 1</name>
<contextid>129</contextid>
<contextlevel>70</contextlevel>
Directory related ... activities ... contained there in ... as per example:
[root@server activities]# ls -d quiz*
[root@sos activities]# ls -d quiz*
quiz_102 quiz_107 quiz_112 quiz_116 quiz_73 quiz_78 quiz_83 quiz_91 quiz_95 quiz_98 quiz_103 quiz_108 quiz_113 quiz_72 quiz_77 quiz_82 quiz_87 quiz_92 quiz_97
and more .xml
[root@sos quiz_102]# ls -l
total 48
-rw-r--r--. 1 root root 57 May 29 17:50 calendar.xml
-rw-r--r--. 1 root root 61 May 29 17:50 comments.xml
-rw-r--r--. 1 root root 132 May 29 17:50 competencies.xml
-rw-r--r--. 1 root root 67 May 29 17:50 completion.xml
-rw-r--r--. 1 root root 137 May 29 17:50 filters.xml
-rw-r--r--. 1 root root 106 May 29 17:50 grade_history.xml
-rw-r--r--. 1 root root 1305 May 29 17:50 grades.xml
-rw-r--r--. 1 root root 533 May 29 17:50 inforef.xml
-rw-r--r--. 1 root root 760 May 29 17:50 module.xml
*** -rw-r--r--. 1 root root 6789 May 29 17:50 quiz.xml
-rw-r--r--. 1 root root 137 May 29 17:50 roles.xml
If one could determine what certain values should be when one restores to a site, one could 'doctor' the xml's ... repackage the .mbz ... and attempt restore. *** BETTER do that on a clone of production first!! ***
OR ... option 2 ...
if you have a site backup of when the moodle was 3.5.x, restore that to a localhost instance. Once that's up and running, access the hidden health tool in admin/tool/health/
Will have listing of problems found and suggestions as sql queries to fix.
Not 100% but might fix your issue enough to make new backups to restore to the 3.7.x.
Think I'd try 'option 2' above before 'mega' effort (which will probably fail whale first time and frustrate one in short order) in the first!
'SoS', Ken