Ah sorry – just saw this! I’m currently using random justified gallery and got it to work properly – I forget if I tweaked any settings. I think I tried mosaic at first and couldn’t get it to work. I’ll see if I have issues once I add new albums but for now it’s fine!
I changed the style of the gallery to square thumbnail grid and now it works, for whatever reason. I’m going to mark this as resolved – I assume it’s a problem specific to my website.