Problems with random: begin and random: end

I have a survey in which the questions of one section should be presented in random order. When I insert random: begin and random: end around this section, the questionnaire behaves erratically, often showing just one or two of the six questions and then jumping to the end. Also, the page: begin and page: end in an earlier section of the survey stop working, and the progress bar starts to show numbers like 153%. Any ideas? I think I have followed all the instructions. 

I reproduce the relevant part of my code below. 



page: begin



l: attentioncheck1

t: textline

q: What are these creatures like?

- {require} Answer



l: attentioncheck2

t: textline

q: What is this individual doing?

- {require} Answer



page: end



random: begin



l: fixity

t: radio

q: Will the same individual do the same thing on other days?

- Yes

- No



l: typicality

t: radio

q: Will other individuals do the same things as this one?

- Yes

- No



l: utility

t: radio

q: Does the individual find it rewarding to do this?

- Yes

- No



l: innateness

t: radio

q: Is this behaviour innate?

- Yes

- No



l: genes

t: radio

q: Is this behaviour in its genes?

- Yes

- No



l: brain

t: radio

q: Is this controlled by its brain?

- Yes

- No



l: biological

t: radio

q: Is this behaviour biological or psychological?

- Biological

- Psychological



random: end