@PocketSand My son is long-term unemployed.
I really think from your last email that you perhaps need to work on your son's social anxiety before worrying about the degree, if you are looking at life skills he will need. Battling away on this course could make his anxiety worse rather then better, and there are alternatives.
An engineering degree is unlike other subjects, because the engineering councils dictate the course content, and at the moment academic ability seems to be secondary to management skills. From talking to son's lecturers, it seems the councils want people who have excellent management skills, so at uni it is assumed they will be able to manage nearly full-time lecture timetable, plus self-study, carry out and write up complex regular lab assigments on time, including assignments working in teams. I think the engineering councils aim to produce industry leaders and project managers rather than deep thinking analysts. (I do think, btw, this is wrong, because they are losing the talents and technical skills of people like your son along the way, and I believe as a country we need more deep-thinking analysts who might have realised, for example, that projects like HS2 were a bad idea.)
Had I known all this sooner we could have chosen a more achievable subject, capitalising on skills he has rather than trying to compensate for those he does not have.
This is why my original advice stands, don't let him go back to uni, in particular to an engineering degree. I am slightly cross they let people resit, as they did in 2nd year for my son, because it's not helping them in the long run. Remember universities are businesses and want your 9k tuition fee money, so they make a bit more money if he stays an extra year. I believe they take in way too many engineering students just to get their fees. In the past departments were smaller and students could more easily access tutors, face to face, not online, and funding did not come from tuition fees.
There are alternative routes to battling through this really hard degree:
Try a degree with less demanding workload and get a higher grade, you will be more likley to get a job, and one you will enjoy, as it will be in an area you have proven ability.
Have a look at 'data science' degrees and job opportunities, its the latest thing and I think may be of interest.
Try a free bootcamp in cyber, software.or similar.
Phone Lotus, or any employer, and ask if they have degree apprenticeships, or if a good maths or science graduate can get a job there.
Try taking a year out of education altogether to travel, enjoy a hobby, join clubs or volunteer, or do some maths coaching, to help get over the social anxiety. Employers really value work (and other) experience, often more than paper qualifications. Go back to uni when you have had a rest. With some maturity and experience there is a chance the life and management skills will improve, and he will cope better at uni as a mature student.
Of course I do not know your son, given a second chance he may actually be capable of managing his time brilliantly and understanding what is needed, but you you might not find out until too late, and ultimately this is the dilemma.