I have a weird problem with my design. Some of the inputs are not connected. From the reports and simulations. all inputs seem to be connected to the external pin, but when connected in the lab, they don't. The most strange is that if the design is re-synthesized and re-implemented, sometimes it really works, without changing any line in the code!. Moreover, when it does not work, the input pins that are not connected are not always the same.