ricovalium, are you seeing any suds during your cycles? Using too much detergent should not cause any leaking unless it results in excessive sudsing. If you are using HE detergent (what brand? liquid or powder?) suds should not be a problem.

Doesn't appear to be excessive suds (though admittedly I haven't stared at a full cycle) and no soap film on floor. We're using Trader Joe's HE detergent. Could a whisker over a tablespoon dose really cause this?

I can't imagine that detergent is causing it, but you need to experiment a bit and watch your washer to see under what circumstances the leak happens so that you can explain it to the repair guy. And maybe you can duplicate it while he is there so that you don't get the same response? They seem to be always quick to blame the user so you need to be armed ;-)

Thanks. Going to try controlled experiments to try to find issue...

1) Overfull load, 2) Undersized load, 2 TBSP+ detergent

I think it just might be the intersection of the 2 that is the issue.