After adding enough new connections, spindump stops giving measurements

After adding enough new connections, Spindump completely stops giving out new measurements. Restarting Spindump doesn't help, but after reducing the amount of connections, Spindump starts giving out measurements again.

No file, test, or entry point is named. Reproduce the failure by adding connections until measurements stop, then reduce the connection count to confirm recovery; trace the connection and measurement handling to identify the limit or exhausted resource. Done means Spindump continues producing measurements after many connections and the behavior is covered by a regression test.

Written by the indexing model from the issue text.