Retention policy does not help when hitting the series limit

We are trying to use influxdb in a memory limited environment. Our data scheme requires to assign a medium number (1000 to 10000) of tag values.

We already found out that this is not optimal regarding the memory usage of influxdb.

Our current attempt is to limit the number of series with max-series-per-database = 10000.
So far, it works as expected. Whenever we hit the limit, new tag values are dropped during import, which is what we try to achieve.

But the key-space of the tag values seems to be not released by the retention policies. Even when the series should have been dropped we cannot insert new entries.
As a result the database looks empty (doing a select * query) but we cannot insert new elements.

This issue can be solved by restarting influxd. After restart we can insert new tag values again.

Any idea how we can overcome this?