Sounds to me like you have a dodgy contact on the camera lens mount. As you have already cleaned them etc. the only thing I can think of trying before you send it away for repair is to get something that's not too hard, such as a toothpick, and just try depressing slightly each contact to see if any are stuck or something.
I have a slight problem with my A7Riii connected with the auto-focussing. Occasionally it will not auto-focus at all and the image remains out of focus. Checking the FN function the focusing tab is greyed out and if I persevere it will say 'This lens not compatible or not connected' etc. I have to remove the lens and refit it, making sure I push the lens hard. This happens with all my lens so I suspect it is the camera. I examine the contacts, cleaned them all and examined the mount etc but all seems fine. Just wondering if anyone else has had this problem and if it is fixable.