It sounds like they are losing power, most likely do to low voltage since they are flickering. How many lights are plugged into the pack and how many packs are plugged into the same outlet? What else is plugged into the outlet the pack is plugged into? If there is nothing but just that pack, make sure it is a dedicated outlet and not shared with another outlet somewhere else.
I also assume its a club of some sort, so it is possible the voltage drop is accruing at the panel/distro if amps are in the same panel/distro. If that is the case, try moving the packs into an outlet not shared with amps panel/distro.