TYPO3 Core

Given the following TSconfig file:

# EXT:site/Configuration/TSconfig/user.tsconfig
options.clearCache.pages = 0

Given the following BE group setup:

• Group Default
  tsconfig: <INCLUDE_TYPOSCRIPT: source="FILE:EXT:site/Configuration/TSconfig/user.tsconfig">

• Group Special
  subgroups: Default

• Group Advanced editors
  subgroups: Default
  tsconfig: options.clearCache.pages = 1

And given a user member of the groups "Advanced editors" and "Special".

This user does not see the clearCache.pages button.

The reason is the order in the resolution of the subgroups, and the tsconfig parsing (see \TYPO3\CMS\Core\Authentication\BackendUserAuthentication::prepareUserTsConfig)
The resolved subgroups are : Default, Advanced editors, Default, Special
For each of this groups, the TSconfig is computed:

# TSCONFIG of group Default
# INCLUDE EXT:site/Configuration/TSconfig/user.tsconfig
options.clearCache.pages = 0

# TSCONFIG of group Advanced editors
options.clearCache.pages = 1

# TSCONFIG of group Default
# EXT:site/Configuration/TSconfig/user.tsconfig
options.clearCache.pages = 0

# TSCONFIG of group Special

At the end, the all TSconfig is parsed, and options.clearCache.pages will be 0.

A possible fix will be that the parser includes file only once.

My workaround was to remove the subgroup Default from the group Special.