Is something wrong with Muun? Trying to send muun to muun Lightning and it is giving this error. 
Discussion
I migrated all sats to Phoenix after Muun being mostly unusable last couple of days, including recently when fees kind of normalized.
That's the way. Although Phoenix also has problems with small channels so it's hard for me to recommend for noobs. I wish they had a feature you could tell, always open 300k sat channel minimum, I'll pay the 1% fee (3k sat) just avoid small channels
always has been, it's an onchain wallet that pretends to be a lightning wallet.
From what I've heard from other people receiving lightning breaks in high fee environment because they can't send you the money onchain from their clogged wallet.
Whereas sending lightning from Muun works you just need to pay the onchain fee