Trouble connecting left and right AirPods together

I have recently had the following problem; Only one of my AirPods (left or right) can connect at the same time. Both clearly work, if I only have the left in the case and reset the case, the left connects fine, and if I only have the right in the case when I reset the case, the right connects. When both are in the case when I reset, it seems to randomly select the left or the right. I am trying to connect them to an iPhone running iOS 18.3.2. This is the usual phone the AirPods always connect to. I have tried leaving them charging overnight to ensure their firmware is up to date. How can I fix this?