Hello,
If you want to create a Process schedule in version 2020.1 and have selected "Once" at frequency type and you want to deploy this schedule to IAM it looks like the sync is crashing. But behind the GUI screen there may be a message that NULL is not allowed in column "occur_every_time_unit" in table IAM.dbo.process_flow_schedule. The reason for this is a difference in metadata between the SF and IAM for this column. In the SF, NULL is allowed. For now I changed properties of the column in IAM.