When visiting some sites on Cromite, Fennec, or IronFox on my Android devices, the Anubis challenge fails with the error "invalid response". I don't recall if there were any other error messages that came up. This only affects a seemingly random portion of sites using Anubis and does not clear up after refreshing, both immediately and after waiting several hours. It's never affected Firefox and Librewolf on desktop, however.

Anyone know why it happens, how to avoid it, or what logs I could collect for an issue report on Github?