All of the following are reasons for implant failure after insertion EXCEPT:

Smoking, uncontrolled diabetes, and periapical pathology near the implant site are all well-documented biological risk factors for implant failure (impaired healing/osseointegration or contamination from adjacent infection). A crown that simply does not reach occlusion is a prosthetic/restorative issue, not in itself a recognized direct cause of implant failure — it's the exception here.