ARES 160Rds Mi-Capa Magazine for ARES SR25 AEG

I've ordered 2 pieces. Both have a slight twist in the metal part making the plastic upper part not fully fitting on it. This makes the insert of the mag a bit stucky. Lucily this twisting is fixable easily.
But sadly both mags of mine has something with the feeding. Sometimes they doesn't feed BB: 1 of 20-30 in single and full auto fire. Have to check why..