@shankar your explanation is perfectly clear, Also, your observation is correct. Up to firmware 1.5 Electra calculated the sign bit position dymamically based on the range. It worked with the devices I worked with. @jigdagod later reported the same issue as you have with the Hydrasynth.
I added the bitWidth attribute that tells Electra where sign bit should be placed. This attribute is available in the upcoming firmware release. You can either test it with the beta release available at New ElectraOne console / Testing needed or wait couple of days. As mentioned in some other thread the new firmware goes out soon.