E00013 Email is invalid authorize.net having random error on recreating ARB subscription

we have authorize.net arb recurring billing implemented on one of our live systems built on asp.net mvc & C#. Now from a few days we are getting report of above error that happens at random, i can create new subscriptions without any issue using auhtorize api. but when i edit a subscription info [we do this by simply dropping old subscription and recreating it from available info]. we get the error invalid email id from authorize transaction response [E00013].

the screenshot is attached below:

i am using standard authorize sdk nuget package and http://ift.tt/2deyhdS as code base for creating new subscriptions. please note the issue is random and we are not changing customer info only date of subscription charge cycle.