People and the processes not caring about writing knowledge down. From no process documentation to no knowledge management tools, including but going way beyond:

* Being OK with useless commit messages.

* Disregard for auditable tracking of issue progress, decision making, design flows, etc. E.g. Anyone having to tackle any existing non-trivial issue needing to be forwarded many email threads and random files.

* Predictable emergencies needing avoidable crunch mode over and over, no knowledge accrued about how the last fixes went.

The more examples I think about, the more it boils down to: any signs of an insatiable gluttony for technical debt should make you think twice. You're likely to be the one paying for it in the end.