QUOTE(TheEvilMan @ Oct 4 2017, 04:17 PM)
Am talking about Bandai Decals, i guess it's a little thicker, after dry for days they do stick nicely, but when i dry them with cotton and leave it for few minutes while working on the decals and i proceed to do other parts, perhaps by accident i would touch the decals, and they either drop or stick to my thumb then went missing, yet i see some people do decals in one go and have no such problem

, now have to find identical decals to replace the missing one
how long you dip the decals in water? if too long, the decal loses it's adhesiveness.
when you use setter, if the decal is too wet the water will wash away the setter, or when you adjust too much the setter becomes ineffective.
and when you use the softener, you cannot apply on the whole decal 1 shot, have to start from 1 edge dry up then the other, and finally apply sparingly on the middle. use too much or 1 shot you risk decal coming off.
regarding doing multiple decal, if the decal is too close to each other that the water may sip into decals applied, better spray a top coat to seal off the applied decals 1st. if not have to make sure the water doesn't touch applied decals.
usually we apply decal part by part before fully assembly, when you work on 1 side just make sure you don't scratch the other. you don't need airbrush for top coat just to seal the decals, any cheap DIY clear coat will do the job. just 1-2 burst will seal the decal and dry quite fast. once you finish the decal you can spray thicker clear coat to even out the edges.
well, i don't build Gundams so this is what i read from internet. all the best.
if water slides are giving you problem, can always use the traditional stickers.