I've been using Mapei Mapeker Rapid Set Flexible Adhesive to tile and I need another bag to complete the job. I went to the screwfix site and found a scathing review of this product. The reviewer claimed that the product is scratchy and will actually scour the surface of your glossy tiles. I haven't found this to be the case and I was wondering whether this criticism of the is justified. Should I get a different adhesive to finish the job or should i get the same one?