MCP failure, yes it may happen.
I've just seen on N.Geografic the accidents with the 737 rudder. The first accident and the incident happend like you said ,the 737 crossed some wake turbulance ,a jolt ,and the plane banked to left or right.
In the third case they were high ,and they had chance. Also ,the problem dissapeard by itself.
So, is the RSEP installed on your plane? This kind of occurence should be reported to aircraft manufacturer ,it may prove very important.
I can give you one example,happened 2 month ago ,big company,west europe.
" During flight control checks,a slight diff in pressure was felt on left ruddr.Then a kick was felt as the rudder was centerred and the Stby rudder light illuminated.After removing panels from the fin it was found that the rudder has not been modified to reflect the aircraft modification state "
Amazing ,right ?.
So ,make sure you report that to tech department,chief pilot,etc...be sure they found what was wrong.