Hi @firda -
Two ping sonars used at the same time with default settings are going to interfere with each other! Some users have had success communicating with the sonars and controlling the timing of pings to avoid interference, but if using ping viewer or ping viewer next (beta) the use of only one at a time is expected.
Remember that the Ping sonar has a 30 degree beam - this is quite a large cone, so using them for heading may require significant separation distance…even operating with them at 90 degrees could result in interference depending on the environment!