1. Severity can be dependent on person or group assessment and his or her knowledge level. it will not cover all source of severity. for example, if we select 4 people they will have limited thinking and based on that all risk may not be covered.
2. Also severity is based on assumption, like if x fail because of y , this can z might happen actually we dont know whether Y is the actual root cause or not.
3. Also good engineering is better than Fmea.
4. It doesn't take in to account statistical data.
5. It only prioritizes and doesn't make it right
6. It acts as reactive tool
7. it does not include supplier and customer
8. Just a document
9. Not linking with control plan, mistake proofing
10. No update once made
11. People may not be serious about the process.