I found this report in Mantis which seems to describe the same error in ILIAS 5.3. Reading the comments, it seems unclear if this was fixed:
https://mantis.ilias.de/view.php?id=24319
If you are still using ILIAS 5.3, please note that support for this release has ended in August 2020. There will be no more bugfixes for this version. However, if this error occurs in a supported version (currently ILIAS >=5.4), you may want to create a new bugreport in Mantis.
https://mantis.ilias.de/view.php?id=24319
If you are still using ILIAS 5.3, please note that support for this release has ended in August 2020. There will be no more bugfixes for this version. However, if this error occurs in a supported version (currently ILIAS >=5.4), you may want to create a new bugreport in Mantis.