They have made 920KB of changes to the code and completely muddied the entire codebase. I debated listing the major problems they have introduced, but I really don't know where to start and don't have the strength to list them all. To sum it up, they clearly do not understand how the codebase works at all. They are willy-nilly making changes without understanding the full ramifications of those changes. Their code is very messy and hard to read. They have broken compatibility with Core so cannot accept patches from Core and are stuck on an old outdated version. They moved core functionality out of their own separate modules and hacked it in all over the place. They do not understand how Bitcoin uses asserts to detect situations where it is running in an impossible state and crashes to prevent exploitation, so instead they straight up removed this entire system putting them at huge risk. They do not have any test or QA procedures. Often developers commit code without any third party review. The developers have no experience developing anything like Bitcoin at all and have crazy ideas about how it works (recently a BU dev tried to convince me CAP theory applies to Bitcoin). Thats just some stuff I can remember off the top of my head.