False Answer While It's True

[rudipratm]

Sometimes mathcaptcha got false answer while it's should be true. I've the captcha to something like this: 7 + 3 = and the answer I type is 10 (as it should be). But it's detected as wrong answer. After the second attempts, then the captcha is detected correctly (with other questions, of course).

Do you know about this, or how to fix this issue ?