Got 998 and was working perfectly. Bought new lakemaster south card and installed update 6.74. Went to lake yesterday and depth would stick at certain depth. Would read same depth until turn unit off and reboot and would again go to depth and stay on that depth. Is it software problem? Run 2 transducers, one in hull and side scan on back of boat. Side and down work, shows depth on down image but depth reading wrong. Help!!