This problem was first detected on a workflow for a custom entity in 2024 R2 and 2025 R1.  I just now tested by adding it to the generic Reassign step on the generic Opportunity Workflow.  Simply edit the step, create a new Action of Create Appointment and save the defaults.  When you test on the user side, CRM throws a DLL error.  This was duplicated by CRM Support NA.  I'm curious if anyone else has seen this.  Thanks.