Trying to restore database from backup with Module ProcessDatabaseBackups PW 2.6.21 throws the following Fatal error: Call to undefined method WireDatabaseBackup::trackException() in .../wire/core/WireDatabaseBackup.php on line 1098 (backup is from version 2.6.10) After reloading the page I get the following error notices: Modules: Configurable module check failed for SessionHandlerDB, retrying... Modules: Configurable module check failed for FieldtypeRepeater, retrying... Modules: Configurable module check failed for FieldtypePage, retrying... Modules: Configurable module check failed for PageRender, retrying... Modules: Configurable module check failed for SessionHandlerDB, retrying... Modules: Configurable module check failed for MarkupCache, retrying... Modules: Configurable module check failed for LanguageSupport, retrying... Modules: Configurable module check failed for LoginNotifier, retrying... Modules: Configurable module check failed for AdminThemeDefault, retrying... Modules: Configurable module check failed for InputfieldSelector, retrying... Modules: Configurable module check failed for ProcessPageSearch, retrying... Problem solved: Divergence in database settings in $config (using 2 different installation dev/master). Apart from this I would expect another Error message in this case.