This is small, the biggest bug in BU has still not been fixed and is not even recognised as such.

i.e. Emergent consensus failure bug

The 'emergent consensus' mechanism means miners can increase profit by increasing the blocksize.

The only thing stoping increasing the blocksize is the increasing cost of bigger blocks due to orphan rate.

To optimise for profit miners will have competitive pressure to reduce orphan rate and that is easily done by centralisation of  mining.

With centralised mining Bitcoin is led to a permanent failure mode as it devolves into a fully centralised system. Centralised mining and centralised nodes.

This is a massive, massive, catastrophic bug that would slowly kill Bitcoin if the network would run on BU (unlikely). This still has not been fixed by Bitcoin Unlimited.