From your picture I thought the failed part and successful one were oriented and aligned the same way, right beside each other along the same “row”. I would definitely print a part like that perpendicular to the LPU and mixer (parallel to the front of the printer), as you suggested.
You can think of it as the part being more “resilient” to longitudinal forces and more easily pushed over by lateral ones, if that makes any sense.
Just to make sure - you used the PEC Pad and IPA on the underside, i.e. exterior side, of the film, right? (You probably already know that you should never touch the inside surface of the resin tank film with anything but the tank tool). Also be careful bits of PEC PAD don’t stick around on the rollers (I’ve seen fibers come off the pads before; often I use a blast of air to make sure they’re cleared).
Are you having better luck after the steps you took and with the new orientation?
I’m still kind of surprised the part failed before the supports were completed. If it were solely due to peel forces I would have expected the failure to occur a little higher up, but admittedly I haven’t seen this specific mode of failure yet myself on the Form 3.