Eh
I won more than 10K at Spin Palace quite a while ago, and I don't recall any suggestion of me being paid in installments.
More worrying is the fact that Mummy's Gold only paid 750 in one go of your 1000 withdrawal. It is worth checking whether the other 250 has been refunded to your deposit method (a card for example). I have had this before when depositing by card, and also when mixing cards and Neteller. There doesn't seem to be a set rule as to what part of a withdrawal is deemed a return of past deposits, and likely to end up on a card.
What makes things even MORE complicated is that even if the deposit that lead to the 1000 withdrawal didn't come from a card, the 250 may be deemed a return of an earlier deposit made by card that you busted out on.
By paying the first 10K, Prime have at least shown an intent to pay, even though the installment plan is far from ideal. You will just have to sit tight for the next couple of months. You can show your displeasure by uninstalling the Palace Group casinos until you have received all payments in full. Once you have your money, you can then ask for an explanation as to why it took so long to begin paying out, as 14 days is far from normal, even if the installment plan that followed is dictated by the terms.
Look on the bright side, you can't lose the entire 22K back next week