Unable to select physical rewards when purchasing supporter packs

Recently picked up the Thaumaturge pack, and ran into a frustrating loop when trying to enter information for the physical rewards.

1. When trying to enter information, it consistently said that a "field was invalid"
2. The only way I found to reset this was to check and uncheck the "Opt out" of the physical rewards
3. When doing this, the information from the "Email" field would be moved to the "Name" field, leaving the email blank (and making an invalid field again)

Sometimes I could correct it and submit after the above, but trying to submit would open Steam to complete the transaction and just crash Steam in the background.

Trying to complete the transaction on the website during this said that I would not receive physical rewards as I had "previously opted out" and would need to contact support.

Rather frustrating, I ended up just giving up and opting out of the physical rewards.