Increasing passive ACU usage on RDS Aurora MySQL Serverless v2 clusters

We have noticed a sudden increase in costs generated by our RDS Aurora MySQL Serverless v2 clusters that we cannot understand, and would like some help in resolving this issue.

Around February 18th, we noticed that the capacity metric on our instances was not decreasing its capacity to a minimum at night when no one was using it. Before this date, our clusters would usually maintain a minimum of 0.5 ACU during off-peak hours. However, after February 18th, the capacity stayed the entire night at 1.5 ACU, and later to 1 after we capped the max capacity at night.

We have followed the instructions recommended by some users and turned off Performance Insight, but the problem still persists. We could not find any queries generated by a user in the logs of the night where no one usually uses the system, only the ones executed internally by RDS.

We suspect that the reason for the sudden increase in costs may be due to an internal change that AWS made to the service. If this is the case, we would appreciate any information you could provide us on this change so that we can optimize our resources and reduce costs wherever possible.

We would be grateful if you could investigate this matter and provide us with a prompt response. We rely on your expertise to help us resolve this issue and continue to use AWS services effectively.

Thank you for your attention to this matter.