tajima tehx-c1501 error help please

hi

i have a tajima tehx-1501. it has the upgraded touch screen panel. for some odd reason i get a 3a6 error. now i have checked for birds nesting etc but it is clean. after having got a 3a6 error again i decided to take the plate off and could see the knife in the open position but would not return back to its closed position and nothing would happen unless i moved it back manually turned of the machine and put it back on again.

is this a motor problem or does the knife position need setting correctly. does any one have any info on how to sort this out please.

thanks