I just received and range tested an Iver Johnson TP22 (DA/SA 22LR autoloader). The gun functioned very well with high-velocity ammunition - and rather poorly with LV stuff - but would only fire about 50% of the time when the hammer was cocked in SA mode. On the DA strokes it worked just fine. I have stripped and cleaned the pistol and did not note any mechanical problems. Does anyone have advice on how I might be able to correct this? TIA!