Over here, if I am in a custom CPlane and call Trim with ApparentIntersections=Yes, I only get one trim for each run of the trim command. After the first pick and trim, I am still in the command, but nothing else will trim until I end the command and start it again. If ApparentIntersections=No, or I’m working in a world CPlane, it works as expected.
In the attached, call trim, be sure ApparentIntersections=Yes, select all the green lines as cutting objects, hit enter, then for the objects to trim, start picking bits of the green lines you selected as the cutting objects. I’m doing this in the Top viewport, but I don’t think it matters, and I’m using 6.0.15125.8091, 5/5/2015.