TYPO3 Core

"Feature Toggles", in "ADMIN TOOLS>Settings" module, has saving problems, if file OPcaching is disabled (opcache.file_update_protection=0).
The "typo3conf/LocalConfiguration.php" file is not updated correctly.
This problem was already reported #59662

The "featuresSave" action, in the "Settings" controller for "install" system extension, loops over all available features and creates/saves LocalConfiguration file for each feature.
If OPcache is enabled and file caching is disabled, each save overwrites the previous one, but with initial features configuration values.

My opinion
"featuresSave" action should save LocalConfiguration file atomically, as "Configure Installation-Wide Options" does via "ConfigurationManager::setLocalConfigurationValuesByPathValuePairs()"

PS: I have selected TYPO3 v11, but the problem also exists in TYPO3 v9 and v10