Basically prior to some time in 8.2 I believe something changed with regards to SetPoint usage. Since that point I've no longer been able to move the party frames in Retail however still can quite comfortably in Classic.
I create a drag frame that I used to parent the party frames too so that the position could be customised by end users. This now results in the following error.
6x ...eImprovedBlizzardUI\modules/frames/party.lua:59: Action[SetPoint] failed because[SetPoint would result in anchor family connection]: attempted from: PartyMemberFrame1:SetPoint.
[string "=[C]"]: in function `SetPoint'
A snippet for this can be found here where you can see i'm bailing out currently if it's retail however the code below did used to work and does on classic.