This is because the sender is unaware of your channel balances and how much to split up their payments properly, since MPP is something the sender does.
I'm a bit unsure why the sender wouldn't eventually find the right split, but perhaps there's a time out issue here. And I'm not sure why it's not attempting to create a new channel instead of trying to fit down the existing ones. Perhaps I misread something or I'm not familar with how you are testing this.
This is because the sender is unaware of your channel balances and how much to split up their payments properly, since MPP is something the sender does.
I'm a bit unsure why the sender wouldn't eventually find the right split, but perhaps there's a time out issue here. And I'm not sure why it's not attempting to create a new channel instead of trying to fit down the existing ones. Perhaps I misread something or I'm not familar with how you are testing this.
https://github.com/ACINQ/phoenix/issues/155