Unfortunately in this case, the axle cap has a flange on it, probably something to do with the ill-fated Phil disk brake. That damn flange is what caused all the problems, and it might make it impossible to put even a brand new replacement seal back on.

I think you may have to knock off that axle cap. It's a press-fit, kinda tight but I have had success knocking it off with a long thin punch down the QR hole from the other side. Heat applied to the cap will help. I would employ it as a "first resort", not a last resort after failing cold. A blow-dryer if that's all you have, but a heat gun like you use on heat-shrink tubing would be better. Heat it quickly and knock the cap off immediately before the heat conducts in to the real axle, that the cap is pressed to, we don't want that to expand too.

I have also removed the whole axle + bearings subassembly from the hub "can" on Phil hubs a couple times. Then you could send just that part to Phil for new bearings.

Removing the axle subassembly isn't hard, on a single-bike hub anyway (dunno if tandem is different). In fact plenty of people have done it accidentally! Just thread on a freewheel, then remove it with a QR skewer clamped down on the FW remover. As the FW threads off, it pulls the axle + bearings out of the can, like a cotterless crank extractor.

Then when PW sends you the refurbished subassembly, you need to press it back in, so that could be the tricky part. I know how to do it with a long piece of all-thread, a piece of pipe sized just right and a couple nuts and washers, but it's a bit hard to explain. Maybe PW can advise you on that, possibly including the advice to NOT try this on your own. Just about any old arbor press will make quick work of it on a bare hub, and I know someone in your town has one, they're quite common in many kinds of shop (even hobbyists), but a press with a deep enough throat to fit a built wheel is a rare thing.

Shipping the whole wheel to them costs a bit more but takes all the danger and uncertainty out of it.