Help with figuring out exercise bike tension fault..??

hello not sure if appropriate place, google search led me similar problem here..

i have universal fitness 795 recumbent exercise bike got free, issue resistance doesn't change.. better half ok .. started looking online , saw seems simple electrical issue of time... tore bike... , saw has motor supposed turn , adjust tension on bicycle wire/cable in turn pulls resistance...

after opening further find there motor turns tension knob attached potentiometer think supposed control or signal when spindle turned level...

when removed gears motor , put batteries in motor turns on , spins non stop.. thinking it's either not getting single stop.. or there trip somewhere keeps running?? tested pot think multimeter following youtube , using ohm setting increasing reading @ different turns on pot.. , when motor going reverse direction depending on turn pot..

i noticed 1 little blue box has adjustable dial appears on it, there appears no continuity between 2 wires on either side when checked.. have no idea blue box , supposed or if there should continuity between these 2 wires..

so after hoping suggestions/opinions on should try checking or insights worse comes worse rig bicycle parts make tension wire adjustable manually.. cool if simple electronic part replacement fix it..

i hope pics i've been describing.. time!!

looks standard servo, easy / cheap replace.  moving magnet used
for electromagnetic braking on flywheel think.

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