Thank you both for your help, I appear to have found the problem.nThere was a face on one of the fluid volumes which should have been a hole for the fluid volume in the centre. It seems that this was causing the interface surface and causing the solver to fail.nI re-did the geometry so that there are only 2 fluid volumes separated by the baffles and this has removed the interface surface.nI have run the solver with the original settings and it's made it to 5,500 iterations and 111 time steps so far without an error so I think it's worked.nThanks again for the answers, I'll update here if it doesn't work but I think I know what the problem was and how to avoid it now.n