Subnet / Private IP not released after terminating a DBSystem

Summary

DBSystem created in a subnet with 2 private IP addresses. After terminating the DBSystem 2 times, we can't launch a DBSystem again.

Content

Hi, 

our configuration (Proof-of-Concept for a customer) using OCI command line interface:

Compute instance VM on Subnet1, DBSystem (VM) on Subnet2 only to run the DBs (test/development environment on request). 

Our Subnet2 does have a 10.0.0.4/30  network (in total 4 IP addresses, of which 2 are usable). When we launch a DBSystem and terminate that twice, we can't create a new one, after 3.5hours of deployment and restoring from backup we get an error, that all private IP addresses are in use. In reality, there is no system running/launched/available at the Subnet2, so all private IP addresses should be available.