i'm having trouble with a CAT C6000 with K25 engine. operator reports forklift won't lift or lower when interlock symbol is flashing on screen. does it once in the morning and works most of the day. then may do it again later. checked seat switch but OK. operator now reported both lift and lower out..and no travel. dash shows interlock flashing and neutral sign flashing as well. can't seem to pinpoint this issue. could this be a problem with the ECM?