Hey,

I have a self-paced reading experiment: participants press a button when they have finished reading the current word and are then shown the next word. For this, I loop over pairs of showing a text canvas and collecting a response; one loop for each sentence.
For some reason, in 90% of cases, the first response to the first item in a loop is ignored. I have no idea why. Any ideas?

```
from openexp.keyboard import keyboard
runs_keyboard = keyboard(exp, timeout=None)

from openexp.canvas import canvas
from openexp.sampler import sampler

import random

lines = """Tiere: Lachs Wolf Gnu;
Kontinente: Afrika Amerika
"""

lines = lines.replace("\n","").split(";")

categories, memberlist = [], []
for line in lines:
    category, ms = line.split(":")
    categories.append(category)
    memberlist.append(ms.strip(" ").split(" "))

error_sound = sampler(exp, '/Users/jona/funk.wav')

blank_canvas = canvas(exp)
blank_canvas.text("")

fdot_canvas = canvas(exp)
fdot_canvas.fixdot()

pre_canvas = canvas(exp)
pre_canvas.text("Number of runs (*10)?")
pre_canvas.show()

rt, critposses = [], []

maxruns, t = runs_keyboard.get_key()

run = 0
while run < int(maxruns)*10:
    blank_canvas.show()
    self.sleep(500)
    i = random.randint(0,len(categories)-1)
    category = categories[i]

    members = list(memberlist[i])
    members_old = list(members)
    random.shuffle(members)
    mismatch = bool(random.randint(0,1))

    mismatch_word = "xyz"
    if mismatch:
        miscats = memberlist[i+1:] + memberlist[:i]
        mismatching_words = [item for sublist in miscats for item in sublist]
        mismatch_word = random.choice(mismatching_words)
        mismatch_index = random.randint(0,len(members)-1)
        members[mismatch_index] = mismatch_word

    members.insert(-1,"und")
    members[-1] = "".join([members[-1],"."])

    words = ["Zur Kategorie", category, "gehören"]
    words.extend(members)

    w_i = 999
    for index, w in enumerate(words):
        if mismatch_word in w:
            w_i = index
            break

    print(w_i)
    cs = []
    for w in words:
        c = canvas(exp)
        c.text(w)
        cs.append(c)

    end = None
    rts = []
    iscorrects = []
    key = None

    continue_keyboard = keyboard(exp, timeout=None)
    continue_keyboard.flush()

    judge_keyboard = []
    judge_keyboard = keyboard(exp, timeout=None)
    judge_keyboard.flush()

    fdot_canvas.show()
    self.sleep(500)
    blank_canvas.show()
    self.sleep(250)
    for index, c in enumerate(cs):
        start = self.time()
        c.show()
        judge_keyboard = keyboard(exp, timeout=None)
        key, end = judge_keyboard.get_key()
        print(key)
        rts.append(str(end-start))
        if (key == "space" and index != w_i) or (key != "space" and index == w_i):
            iscorrects.append("1")
        else:
            iscorrects.append("0")
        blank_canvas.show()
        self.sleep(100)
        key = None
    run += 1

    judge_keyboard.flush()
    continue_keyboard.flush()
```