Using tap tempo on Repeater

[Mountain Man <mtman@cloud9.net>]

I've been using my Repeater for a few days now and absolutely loving it,
although I'm seriously bummed that I don't have a "vintage" model with
the upside down card (does the fellow who was complaining want to double
the value of my 'peater by trading cards? <g>)

There are a couple of things that are still eluding me.  One is the use
of tap tempo.  I haven't been able to get it to work as I expect.
Here's a sample scenario:  I start with tempo dialed in at 72 bpm.  With
the 'peater in User sync, and tempo lock "off", I tap the the "Tap
Tempo" button on every other blink - expecting to lock on about 36 bpm.
What happens is that the tempo shifts slightly after several taps, say
from 72 bpm to 70.5, for example.  I am able to dial it down to 36 bpm
using the tempo knob, but not by tapping. I've tried different
combinations of sync mode, and tempo lock - none of them properly lock
onto the tempo I'm tapping.  Have others had this problem?  Do I have a
buggy unit?

Thanks,
Elby