This can only mean that the other insurance have not paid their share of the total claim. In a 50/50 claim the total losses are added up and split 50/50 between the 2 insurance companies. If person A had losses of £500 and person B had losses of £10,000 the 2 are added together and each side pays £5250 . Not fair to person A but great for person B , but as you can realise, over time it all evens out for the insurance companies and they the save time and expense of chasing claims through the courts.