Filtering could potentially oxidize the beer. Oh, thanks for the reminder. I bought a bottle of Cellar Science Clearzyme and have been using that as well. But it seems like another situation where if a certain group of conditions align just so... this product does not clear the beer. The same is true (IME) with gel. If there is a stubborn haze that is not going away then it's not going away. I have had many batches come out clear when Clearzyme was used but my guess is that they would have come out clear anyway. Whatever it is that I'm experiencing is definitely a process-based issue... water, mash, boil, pH, etc. but that's frustrating because I try to be oh-so-consistent on every batch I make.
I have great success with BTB, whirlfoc, and polyclar VT in the kettle.
Clarity ferm in the fermenter.
And clear beer draught systems in the keg with gelatin.
Clear beer in 12 hours.
Every step of the brewing process has the potential for oxidation. Just running the beer into the serving keg can introduce O2.
I will be filtering 20 gallons of Pils in a few days. It is expected that there will be no issues. If there is any problem resulting from filtration, you will be the second one to know.
The very slight chance of oxidation (if it really exists) will be more than offset by the benefits.
edit: Our beers were always filtered in a previous brewery. There was never any issue with O2 off flavors. The filter set up was 5 micron, then 3 micron. It worked well, very well.