You receive an error after manually deleting a replica VM.
The replication job is still mapped to the previous replica VM. An error is produced when Veeam attempts to access the invalid object.
Unchecking the Low Connection Bandwidth (Enable replica seeding) checkbox does not clear the values held in the seeding /mapping settings, if mapping is left enabled when the box is unchecked. The map must be cleared before unchecking this box.
If it is not already, check the box to enable replica seeding in the Name section of the job settings, then click next until you reach the Seeding options.
In the mapping options, highlight the affected VM and click the remove button.
After this you can disable Replica Mapping, and Low Connection Bandwidth (Enable replica seeding)
This will now allow Veeam to create a new replica VM.