Had this problem twice now, the LEDs I've got seem a tiny bit loose for the cluster sockets. Maybe the cluster plastic is a bit deformed after all the Canadian winters and hot summers?
How can I keep the LEDs in place to prevent them getting loose and flickering/strobing? I used duct tape

but now about three months later one of them is flickering again. This is not an LED problem for sure, it's because they are loose. We all know what a pain it is to take out the cluster so I would prefer a cheap long-term solution