The following output shows that the /geometry/test/run UI command is repeated in all threads. That does not seem necessary. Should it be SetToBeBroadcasted(false)?
G4WT7 > /geometry/test/run
G4WT7 > Running geometry overlaps check...
G4WT0 > /geometry/test/run
G4WT0 > Running geometry overlaps check...
G4WT2 > /geometry/test/run
G4WT6 > /geometry/test/run
G4WT6 > Running geometry overlaps check...
G4WT4 > /geometry/test/run
G4WT3 > /geometry/test/run
G4WT5 > /geometry/test/run
G4WT2 > Running geometry overlaps check...
G4WT5 > Running geometry overlaps check...
G4WT4 > Running geometry overlaps check...
G4WT3 > Running geometry overlaps check...
G4WT1 > /geometry/test/run
G4WT1 > Running geometry overlaps check...
G4WT0 > Checking overlaps for volume chamber:3 (G4Tubs) ... OK!
G4WT7 > Checking overlaps for volume chamber:3 (G4Tubs) ... OK!
G4WT2 > Checking overlaps for volume chamber:3 (G4Tubs) ... OK!
G4WT3 > Checking overlaps for volume chamber:3 (G4Tubs) ... OK!
G4WT6 > Checking overlaps for volume chamber:3 (G4Tubs) ... OK!
G4WT0 > Checking overlaps for volume vacuum:2 (G4Tubs) ... OK!
G4WT7 > Checking overlaps for volume vacuum:2 (G4Tubs) ... OK!
G4WT2 > Checking overlaps for volume vacuum:2 (G4Tubs) ... OK!
G4WT0 > Checking overlaps for volume CsI:1 (G4Tubs) ... OK!
G4WT0 > Geometry overlaps check completed !