I am having a bit of a problem keeping a set of new Bachmann F7 A&B units coupled. This is the N Gauge Spectrum set. I have not converted it to MT's yet as I am working on the track and wiring right now. I am running a test train with 8 40' cars and a caboose The A unit disengages at random points around the layout. I was looking for a bump or a depression that might be causing some uneven stress but that does not seem to be the case. When the units disconnect the coupler on the B unit is in a "raised" position and does not go down until I push it down. After a couple of minutes it goes back up. (spring problem?) Is there anything short of changing out the couplers that I can do to keep the train connected at least until I have the time to install the MT's? Thanks.