I have looked through the bug reports and so far have not noticed any comments with regard to sensor ranges. In my latest game (v1.10.027) I created a cargo ship based design with a sensor range of 23 showing in the ship builder screen. I had all the techs relating to Sensor ranges and had built all the projects,all of my ship designs at that point had only the base sensor range (3 I think) but with the special projects could see a total of 15. I launched this massive spyship towards the AI's territory, low and behold instead of a range of 35 it had a sensor range of, you guessed it, 15.
Are the sensor ranges maxed out at 15, or is this a bug?