You have to learn how to make an exposure test so you don't under or over expose your stencil. You have evidence in your hands with the sticky emulsion. All emulsions are like poly-resin glues and will be sticky when wet. If you crosslink them with a sensitizer, they resist water.
Stencils are easy. If it washes out, or peels off the mesh, it wasn't exposed to enough UV-A light. Unexposed stencil should wash out easily.
If the image is hard to wash out, it was exposed to heat or UV energy and has started to cross link.
Test to see if your positive is blocking UV light. It some UV light leaks through the the positive, it can prevent the stencil from washing out in the image area.
The next time you expose, attach a coin to the stencil which will not let any light pass.
You are using a diazo sensitizer which changes the stencil color as the UV energy activates it. SBQ stencils are MUCH faster but there is no color change, so I suggest you keep to the diazo.
All exposure questions are answered with a stepped exposure test which is essential to any screen maker.
You do a series of 'stepped' exposures on the same screen, then JUDGE the proper amount of exposure.
Exposure slide show and 2 minute video
Support Menu of Screen Making Products
Notice they also have 2 general videos on capillary film and direct emulsion under the 'general' tab. Watch those movies to learn how to reclaim a stencil once you are done with it.