TS can not be saved in template module
I just have installed TYPO3 that way:
composer create-project typo3/cms-base-distribution typo3test dev-master
Then I have added one page, assigned a site-template to that page and included CSC. Nothing more, no additional extensions.
If I edit TS over template module I can't save my changes. I have changed the page.10-part to page.10 < styles.content.get and pressed save. The old TS was displayed again. Same with Save and close. Interessting: CMD+S works.
If I edit my TS over list module everything works like expected.
I have opened my developer toolbar of the browser and I can told you, that the old (unchanged) content will be send via POST and not my changed values.