As with all things plumbing trial and error is the rule. With a new bobbin and new O-rings that leaves only some sort of damage or contamination of the O-rings, or the bore into which the bobbin fits or your suspected alignment problem.
How much leakage did you have? Drops or a gusher? A seep or drops. Did you inspect the bore for damage or contamination prior to re-assembly? Did you lube your O-rings with something to make sure they didn't twist or become deformed while installing them on the bobbin or while inserting the bobbin in its bores?
Just some thoughts.
Hope you are able to remedy the situation.
Gary S. Silver s/v Liahona Amel SM #335 with 160 l/hr Dessalator water maker with re-engineered inline continuous EC (electrical conductivity aka salinity) monitor with alarm and manual control switch for the save/discard solenoid.
Dessalator took a rather simple system and totally screwed it up by attempting to automate it and then not monitoring their vendors to assure they were providing the proper circuity to do what was promised. In case some on this forum aren't aware, the Dessalator water makers of my vintage of boat were installed with sham good/bad water sensors and sham circuity for monitoring water quality. New owners be aware of this and make certain your system has appropriate water quality measuring capability.