Problem with some users not seeing branching options

[Ginnypig]

Good morning,

Really hoping that someone can shed some light on this odd problem that I've been having of late.  

I created a MS forms survey for people to select what sandwiches/salads they'd like for events at the school in which I work.  I have created several branches (eg. Q1 is 'Would you like a salad or a sandwich?')  It goes through (I think that it's around 13 questions in total, as it will take you to a different section, depending on what you picked for each previous answer). 

The problem that I'm having is that about half a dozen or so staff members just don't see any branching options.  Doesn't matter if they pick sandwich or salad, as soon as they select the option, it says 'Thank you for your submission' and closes the survey.  So I have to sift through the hundreds of replies to find the ones that don't show any fillings for their sandwiches, to email them what they'd like.  Our IT department can't find anything wrong (it works for 95% of the staff, just not these couple).  They've tried different PCs, so we know that it's not their computer that's causing the issue.

Has anyone else come across anything like this before?

Thanks for any help that anyone is able to give :)

[#2]

@Ginnypig - you mention that they have tried different PC's. What about different browsers? Are these people using something different to everyone else? I don't know of any known issues, but perhaps if they are using an older version of something (I.E, Firefox, Chrome etc.) that might be making a difference. 

[#3]

@Megan_V_Walker Thanks for the reply; I'll check with them, but I don't think that they will be using different browsers (AFAIK everyone in school has to use what's installed on their PC - which is Internet Explorer/Edge - depending on if they're on Windows 7/810).  I'll drop them an email, but won't hold my breath.  Would be amazing if that's all that it is though!

[#4]

@Zhongzhong Li