Use with Olympus E-PL3 difficult

I bought myself this favorable filter as always top protection for the lens of my E-PL3. The part is sold under the brand name POLAROID, but comes without any doubt from the same production like any other no-name filters. The optical impression as to remuneration and the mounting ring is good. Nothing stuck or wobbles. Also no streaks or stains in the glass visible. However, problems came in the use of the filter with my camera on. Several times it was not possible to move the camera with the filter attached to focus. Apparently, the AF system of the E-PL is irritated in some way by the filter. Whether this will be caused exclusively by this filter, or is a general problem of the E-PL, I can not judge