Strikes me that there is only three explanations as to why this might happen.
Accident
Ignorance
Sabotage.
The fact that its happening regularly would likely rule out accident .
There seems no logic for regular sabotage, though if your "real" clan happened to be a rival ,or your next opponent that might be useful.
Not sure how you fix ignorance.
Knowing who was doing it might be beneficial.
An alternative solution would be for the game to require authorisation for accepting the boost.
Who knows which is the easiest to program, or how high a priority it might be.
Monitoring who is on line and when seems problematic, wouldnt someone also have to be on line at the same time the unwanted boost occurs?
How do you work out who is on line anyway, as the activity indicator doesnt seem to be of much value?
You must be working out when you want to upgrade to finish,might you be able to adjust this time to later on in the event?