For some reason I find it very difficult to get Skritter to recognised the downward vertical strokes in these characters and words containing them. For example 翻 and 桃.

I have tried drawing it slowly, drawing it fast. Tracing it carefully. Everything, but for some reason I always struggle.

Any ideas? Is it my fault or should I submit a report?

It is not your fault. This issue seems to turn up every once in a while (though, for me at least, generally not with downward vertical strokes). What helps is to find a way to draw something vaguely reminiscent of what should be drawn (but is usually miles off). That almost always works. But it is a pain in the rear that it happens in the first place. It is as if "raw squigs" have been turned on while they are not and even perfect tracing does not resolve the issue. All you can do is trace about a dozen times until it finally does accept your trace.

Will try going crazy on the strokes :) Thanks!

I often have problems with 司, sometimes it works if you draw 'smaller' size