As I stated to you in our PM I really highly doubt it's killing your Clean up Crew. Watchman Gobies required Loose LR
rubble or any rubble they use to build there homes. Whats probably happening is he's building his Burrow with your clean up crew thinking he can use them for rubble? Him and his little buddy are jamming them underneath your LR
making them stuck and can't move which is causing them to disappear and Die. Like I said you probably want to check underneath one or to of there burrows and see what's underneath.... I might be wrong but it sounds like thats what's happening....
Check out this link about Watchman Goby