The following error appears several times in stdlogs:
Alias (....) for Session (...) was not indexed
Session id (...) for Session (...) was not indexed
SDM 17.3 and 17.4
The message is more of a warning which can be ignored. The message just says that the session was already removed from the list and we are trying to remove it right now. It doesn't change the execution path in any way.
These messages will be changed to WARN instead of ERROR starting from 17.4 RU3