wrong output

For 2.5V output, the resistor value on VFB pin should be 19.1K ohm. Check if the resistor is correct, and no problem with the soldering, etc. Thanks.  

the resistor value is right. the problem is its output voltage is not a constant value. it changes between 2.5V - 5V .  soldering checked no problem.

its strange that we used three modules,just the 2.5V output appears the problem. layout is the same. 

can you leave a call or email that we can contact each other  quickly. my phone is 18610740667, my email   henry.he@hywitech.com

Hi， Chaz，the problem is very important to me, and i think its better to talk on email or phone.  hope your quick reply.