I work in a stone factory and we are currently having trouble working with epoxy and gluing the mesh back to the stone. So that after wetting the stone, the mesh behind it is easily removed like plastic. All the things about weighing and mixing epoxy have been respected. We have tested many examples of epoxy types. Could this phenomenon be related to epoxy aging and the effect of water on it? Keep in mind that the water used in the stone factory contains a lot of solids and suspended solids.
I have searched and searched for a good water soluble glue that you can use instead of epoxy to glue the mech on the back of your stone. There are some you can try but I am not sure they will work for what you are doing. If you are using a solvent-free epoxy it has an unlimited shelf life and this should be fine as long as you store the epoxy in sealed containers. Other than this you will need to talk to the company who sold you the expoxy. I sounds like you did not have an issue and it was working well for you for a long time. It appears that this new batch that you have gotten is the problem.
According to the article, water will soften the glue and cause the mesh to separate. homeguides.sfgate.com/
I am saying this with all due respect, ecause this sounds like a very serious question that requires a very technical answer.
I would think this question needs to be answered by a chemist who can offer input on after looking at the actual items and the actual situation where this is occurring.
Personally, this is one situation where I would not take any crowd sourced information or information from someone who is not trained in working with epoxy, mesh and stone AND has an intimate knowledge of the workplace and the environment in which this work is being done.
I hope your workplace can get this resolved. It sounds like it could be a safety issue and that clients could be quite unhappy if the product is not as it is supposed to be.