I think it might be related to this report in issues: https://issues.adblockplus.org/ticket/253
(of which I also have the same experience too including with Playstore).
Note: 15 months logged, admitted to be a problem by "rjeschke" and made priority 2 with the words
This is an issue with our integrated 3rd party proxy code, we're going to address this issue as soon as possible.
And that was NINE MONTHS ago (6 months after logging) and nothing done on the bug since.
So I'll just accept that the bug exists and not to expect change. (After all, it is a FREE product so I cant complain or insist).