The fix for all of these is the same discipline:

• rate on objective, verifiable criteria rather than memory.

• Keep a year-round, date-stamped critical-incident log so the review reflects the whole period, not just the last few weeks. Separate factual description from interpretation — record what was seen and heard, not a conclusion about it.
• When rating multiple staff, evaluate one competency across everyone before moving to the next, which sharply reduces halo and horn effects.
• And actively ask yourself what evidence contradicts your current impression of an employee before you finalize a rating.