From what I can tell of the picture, the scrap is similar to gold plated fingers, in this case I would not have used aqua regia.
If solder or tin is involved in these scrap parts the tin will create problems.
Some circuit boards also have copper traces in inner layers of the fiberglass on circuit boards, (I do not know if the ones you have do or not), also copper traces under the solder mask on circuit boards, or pieces of circuit boards can be hard for acids to reach, bubbles of the acids attacking the the metals under these layers can block fresh acid solution form getting under these layers, metals like copper left in between the fiberglass layer or under solder mask can cement values to them.
From what I can tell from the picture, the parts do not have traces between layers of the circuit boards, and I cannot tell but it does not look like you have solder.
It looks basically like you are working with gold plated fingers, if this is the case you would have been better off using another recovery process to dissolve the copper and recover the gold as foils, leaving you with a more clean gold metal to refine.
It looks like you have metals left on the pieces of circuit boards, copper and gold, the copper left would cement gold back to the copper.
Now to the problem as I understand it, you have gold in a solution of aqua regia, it also sounds like you may have used way too much acids, especially nitric acid, from what I can tell some of your gold is in solution (with copper, and possibly some tin), and there is still copper and gold left on the remaining pieces of circuit boards.
I do not see where you have removed excess nitric acid before trying to precipitate the gold from solution, if you have free nitric acid in solution you cannot reduce the gold with a chemical reagent like SMB, the free nitric acid would just redissolve the gold as it tried to precipitate.
As I see it you have a couple of choices here, to recover from this batch, you can add back the pieces of fingers (with the gold and copper foils add heat and let these react with free acids),dissolving more copper and gold into solution, until all of the acid is consumed or no metals remain undissolved, after this you can remove the fiberglass pieces, filter and heat the solution to vapor off remaining nitric in an evaporation process, (adding a little H2SO4 to help precipitate lead later) and aid in the evaporation process, and or, use sulfamic acid to remove free nitric acid, and then try again to precipitate the gold, before the precipitation process diluting the solution, and letting it sit overnight for insolubles to settle out, decanting and filtering the solution before adding your reagent to precipitate the gold, (using your stannous chloride as a guide), if this fails use copper to cement values out of solution.
Then treat the solutions for waste, save the recovered materials, and put up the acids in a safe place,, shut down the lab for a bit, and study, to get a better understanding of how to proceed to recover and refine your gold.
