My friend had a 1 ac pond built last Spring, filled about 75% last year, and with the mega rain we just had [7-12"] it filled and then some. He discovered a leak beneath the spillway - small rivulet, but obviously super distressing. Contractor did install anti seep collars, but water was still seeping through along the pipe somehow.
This same friend is the one with whom I shot the video for the polymer application, and I offered him some of my leftover product. He packed the area of the rivulet with clay, then applied the polymer. Checked today and while the water level remained static, the leak was stopped.
So, that's some more good news. Again, however, I would like to learn how long these seeps remain fixed on average so we know what we're getting into long term solution wise.