One users audio being suppressed and others' not

Hi,

We have an informal weekly Zoom chat with typically 6 participants.  For some time now, one user's audio is completely suppressed when any other participant is speaking.  This does not happen for the other participants who can all talk at once and be heard (I said it was informal!).  It means that the user with the problem simply cannot "break into" an ongoing conversation and it is very frustrating.  The user with the problem is using an iPad (but so are some of the others, so it is not just that).  Anyone had/having similar problems?   Any ideas for a solution, please?