My shower tray leaves a small water puddle not every last drop of water voids to the waste.
This is normal and not a problem or fault. To accommodate expansion and contraction of heat variations, your tray floor is made slightly larger to avoid possible cracking of the finished acrylic surface. On finishing your shower you need to leave the door(s) open to vent the cabin and prevent possible build up of mould or bacteria. The puddling effect soon clears by evaporation. Additionally, usual cleaning is required after every few uses, as with a bath these are simply mopped away with a clean cloth.