I've been practicing Morse code for a few months now using LCWO and can comfortably copy at 8-10 WPM. I'm hitting the dreaded plateau that everyone talks about and having trouble pushing past 12 WPM. That's why people experience a "plateau" at 10 wpm, and don't see any progress for weeks or months. Those who finally get over that "hump" and progress beyond 10 wpm do so because, through constant practice, they have begun to copy code by reflex instead of by thought. I know the goal is to eventually reach 20WPM for contest work and comfortable ragchewing.

What techniques or practice routines did you use to break through this barrier? Did you stick with random groups or switch to plain text?

The key is avoiding that lookup table approach your brain wants to use. Morse at 5 wpm and Morse at 15 or 20 wpm are completely different critters, and you don't want to waste time on the wrong one. I switched from random character groups to plain text copied from news articles. Your brain starts recognizing whole words instead of individual letters - that's when the real breakthrough happens.

I had exactly the same problem around 10 WPM! What worked for me was using G4FON with higher character speeds but slower word spacing (Farnsworth method). you're letter spacing may be set at 8-10wpm to start out with while you're actually learning the characters at a target speed of 20wpm. This method is recommended by the ARRL and is implemented by many applications used for Morse Code training.

Don't give up - that plateau is normal! I practiced 15 minutes daily with W1AW code practice sessions. The QST text really helped because it flows naturally. Soon you forget the sounds of the letters and hear whole words instead. With more and more practice your brain doesn't even think, you are writing down or typing the text without concentrating. Took about 6 weeks to break through to 15 WPM consistently.