When you say bottom plate what exactly do you mean and tape which contact strips?  Thank you

I purchased a 89902 vanderbilt tender this week to replace an existing tender that was still working (both forward and reverse).  I just wanted a vanderbilt to replicate a local engine.  So I guess my problem is this new tender once plugged into my 2-8-0 consolidation engine will only run forward and not reverse.  But if I use the old tender it still works forward and reverse.  Anyone know of this problem and/or have any solutions?  Thank you!