The fix for EZP-23513 ( see https://github.com/ezsystems/ezpublish-kernel/pull/1087 ) deprecates/removes the CustomTags pre-converter in favor of a new Expanding converter.

This should be briefly documented in the ( 5.4.2 / 5.3.5 ) release notes, given that it is a service that may be extended/overridden to suit custom project needs, and may stop working properly after upgrade.