I remembered you'd posted something about this issue! I just got my bulls estream evo fs3 27.5 with a brose motor and it does the same thing, assist to 19 but definitely cuts out before 20mph. Certainly not a deal breaker, but I'd like that extra mile! My haibike sduro Yamaha definitely gets to 20, and the easy motion bikes I've owned previously both pushed over 23 before cutout.