Zavato,
Just noticed this.
Your mistracking is most likely caused by the 45 presenting the cartridge with the problem of tracking a groove which makes the stylus accelerate at a greater rate. This puts it at the edge of its tracking envelope, therefore the influence of the skating force (which is always present in a pivoted arm) more apparent, resulting in distortion on one channel.
Normally, with insufficient anti-skate, the VTF is enough to cope with most groove modulation. When there is more energy in the system, that is not the case and shows up the imbalance in downforce on each face of the groove, which anti-skate is designed to compensate.
Omsed,
you said
when you think you know it all start looking for your mistakes!
Have a look a R.J Gilson's paper in Wireless World Oct 1981 for some more reasons why you might wish to increase antiskate disproportionately as the arm approaches the inner grooves. Also, watch you don't fall into the trap of regarding anti-skate as a setting governed by a "I can't hear a difference with anti-skate, so why bother using it" attitude.
As an aside, regarding 45rpm records, if we had been talking about 7" singles rather than 12" LPs, that is another thing altogether. (see my blog
for
more on this and on anti-skate generally.)