I'm trying to send myself a small amount of sats from Phoenix wallet to my Sphinx wallet / app. I've tried a few times over the past few weeks and I keep getting the same error.

I create an invoice for 50-100 sats on Sphinx and get the 'lnbc' invoice string and copy it to the 'send' dialog of Sphinx. When I hit send, the tx always fails with the following error message (in Phoenix wallet):

"onion per-hop payload is invalid"

Can anyone advise what I'm doing wrong?