I am assuming the decals you are using Jason are of the waterslide type. Do the San Juan decals have a lacquer coat applied over the printed image as supplied ? If not, which is unusual but not impossible, then you may experience the problem you have with the print smearing or "lifting off", especially if you are "working" the decal in its wetted state with solvents. You might want to ask the supplier if this lacquer coat should have been applied and might be missing. Or this coating might be damaged or deleted in some way, even by the solvent you are using. There is also a risk of distorting the decal when manipulating it in any way once you have applied a decal solvent. Depends on how sensitive its material is to those solvent(s) used.
How old is the decal sheet you are using ? Old stock waterslide type decals are prone to cracking/curling and even whole or partial disintegration when decal placement products are applied, or even just in separation from their backing sheet. Use of a heat source, hairdryer, will only exacerbate this problem. Some decals' carrier and lacquer coating do not respond well, if at all, to proprietary decal solvent and setting solutions and can also be the cause of curling. You should always experiment first with a redundant, if available, part of the decal sheet to see how it reacts to the products you are using. Or take advise from the manufacturer on what to use.
If you are not sure Jason of the basic construction and print/coating sequence of a waterslide decal sheet it is as follows - Absorbent paper substrate - Then, adhesive and carrier film is coated onto/printed on to it. It may cover the substrate sheet completely or be printed to conform only to the outlines of the individual design items to follow - Next, printed design, one pass if a modern inkjet type or multiple passes with more than one colour if offset printed or with a printer that requires more than one pass to reproduce the image - Finally, lacquer coat, read as as carrier for its application. With this whole process you can end up with a decal that in terms of material composition and thickness is quite resistant to solvents and applying over fine relief detail. There is no plastic film as far as I know normally used in the process, you usually only find that with self adhesive decals in my experience. Gloss coating of the surface for the decal to be applied to is only done to "hide" the carrier film, it has no other function as far as I am aware.
Some waterslide decals are made so the laquer coat can be removed, with care, so that you leave what appears to the naked eye, a "tampo" printed appearance, but that only works when you are using solid block designs with no show through and with the adhesive/carrier film printed as a close match to the individual decal outline shapes. I trust this helps you Jason in diagnosing and resolving the problem you are having. If all else fails contact San Juan.