I've now seen this on two clients and my own system now.
Sage 100c 2017 Advanced update 1
The build search index utility can be set to run via the task scheduler in the middle of the night.
It seems to be running as expected however it leaves a running session in the master console (no launcher session, but it utility is listed as still running). Right at this moment I see 6 sessions of it. I assume that is one for every day it has run. You can't kill them from the master console. You pretty much have to shut down Sage 100 and then use the task manager at the server to kill the stranded sessions.
I haven't spotted anything in the knowledgebase about it.
Anyone else seeing this and have any thoughts?