Resource is not empty

What causes this issue?

An application program called a COM routine. This led to the following
error:
For bucketed plannable resources: The Boolean attribute
'overlap_buckets_allowed' may only change its value from true to false
if the resource is empty.

How to fix this error?

Contact your system administrator.

Procedure for System Administrators

Contact SAP Service. Inform them of the application component in which
this message occurred.
You should also specify:
The message number
Return code 17145 (om_sl_new_ovlap_bck_alw_bt_occ)
Error code COM Core

Error message extract from SAP system. Copyright SAP SE.