A Second Medical exam requested by CIC after 6 months

[didalili]

I have applied for visitor extension for my mom in March 2016, and my mom has finished medical exam as CIC requested, and CIC approved six months' extension. Now I am planning to apply for the second extension for my mom. When I was filling the questionnaire on CIC website, I answered '"yes" to the question "Have you had a medical exam performed by a CIC authorized panel physician (doctor) within the last 12 months?" However, I found out that CIC still request a medical exam for this application. I felt confused, because my mom just did an exam this March, and I thought that it should be valid for 12 months. So I am writing this post to see that is anyone undergoes the same issue? Is medical exam required for every visitor extension? Thank you very much.