EOS R5 Tech Help

Canon UK have just had my R5 for the past couple of weeks and returned it with no fault found. I've just messaged them tonight and have copied the message below because I'm sure some of you with more knowledge of the R5 may be able to point me in the direction of a solution. I'm sure its something simple I'm missing......

"My camera has just been returned from repair under ticket number: XXXXXX and it has the same issue that I sent it with. It may be something simple that I am missing but the issue is that I suddenly started getting the Blue focal spot when using any lens (100, 24-105, 70-200). I have checked and double checked that I am in One Shot AF and I'm using AV mode, so I am definately not in Servo. I should be getting the green confirmation as I have done for the past 3 years. I haven't altered any other settings, to my knowledge and have tried resetting the camera - to no avail. I've also checked all the lenses are in AF and not MF. What else can it be please?"

Thank you for any advice.