I have personally spent entirely too much time looking at this screen!
I find the Blockstream Green Lightning Wallet slow and buggy. More like alpha release than beta. I am playing around with a 90K Sat channel and mostly ignore it as transactions are slow or fail a lot in both directions, but especially send. I have not tried to close the channel for fear of what your are experiencing.
Yes, I confirm. The sending speed is also very slow. I saw this screen for quite a while before getting the error message.