I've just tested to send to my other wallet (same PC) with enough inbound capacity, and it also failed to send with the same error.
I never had any problem with sending and receiving lightning funds (testnet) to others, though.
I had an intuition that running both wallets on the same PC might have had something to do with it, but I dismissed that notion. I'll try running one wallet on the VM and see if that works. If not, I'll use a laptop. I'll report what I find.