Qualification for this response:
Don't run Windows but do know there are some differences and issues related to platform upon which Moodle runs. **Invite any Windows expert** to jump in here and correct me IF
I'm suggesting something in-correctly.
Just trying to help out ... having 'been there done that' before ... ie, new to Moodle and having an issue.
Soooooooo ... here we go ...
The temp directory (contenhashed named) should have contained a moodle_backup.xml file.
IF it did not, the backup failed and nothing in the temp/contenhashednameddirctory is of use other than clues.
Math courses probably use formulas which are generated by things like LaTex - dunno about Windows, however. Those are images (small gifs, I think). So that's potential area for issues. Math courses might also include quizzes that are more complex than other curricular area quizzes/test. Inspect the courses and look at Quizzes - test banks, etc. In your version of Moodle, when you backup a course, and quizzes are selected to be included in the backup, IF I recall correctly, your version of Moodle had a 'feature' whereby each quiz backed up actually included the entire quiz bank ... so one had multiple copies of the quiz bank to be backed up. Thus, increasing the memory/processing time limits, etc. for the backup.
If you try another backup of one of those that failed, see what's in the quiz.xml as well as quiz directory.
One thing you could try as an experiment is to make a manual backup of one of these troubled courses and de-select every activity that is a Quiz - thus, you have a backup of everything else. Exclude users in this test backup. Name the backup file with -nq- (no quiz) at the end of filename (just before the -nu (which Moodle adds to the name for 'no users'. Doing so will help prevent confusion having multiple backups for same course.
Does the above backup complete? I suspect it will and it will happen quickly.
Then do it again, this time de-selecting all the other activities accept for the quizzes.
Does that one complete? Think we've then narrowed it down to a backup of Quizzes/test issue.
BTW, no fix for version 2.3.x.
Debugging
https://docs.moodle.org/22/en/Debugging
link says 22 there is no link to 23 but 22 should be close to what you need.
DB - MSSQL
https://docs.moodle.org/29/en/Installing_MSSQL_for_PHP
says 29 there is no link for your version 23
Assume it to be similar but maybe not.
There are others on this system who are more Windows oriented and I invite them
to jump in here t assist you with that.
Comment: some of the issues with 2.3 one cannot fix. It's old code and that version is
no longer getting any fixes/updates ... not even for security issues.
The only way to get fixes is to keep the version of Moodle up to date - at a minimum, to a supported version of Moodle ... which today is 2.9.x (latest and greatest), 2.8.x (which is the version I'd recommend right now). 2.7 is a long term version - but it's Moodle's definition of LTS - to Moodle HQ that means updates for security fixes only. In your case, don't think it's a security issue.
Hopefully, upgrading to a supported version will correct the issues ... fingers crossed.
Before you upgrade or attempt to do so, take a full backup of the site. Full backup is comprised of a zip of the code directory, a zip of moodledata and an SQL dump of the DB. Might also note the locations of the moodle code and moodledata etc. if one has to 'roll back' the site.
Also, before you attempt an upgrade, read up on upgrade process.
https://docs.moodle.org/28/en/Upgrading
link says 2.8 ... there is no longer a specific link for your version but process should be same/similar.
'spirit of sharing', Ken