Issues with CiviCRM 5.27+

[bjendres]

Unfortunately, CiviCRM 5.27 and following broke the compatibility of the CustomField API(3), see XCM-68 and CORE-1996.

If you're using CiviCRM 5.27 and up you will have to upgrade to XCM-1.8-alpha2 or higher to avoid the issue.