My experiences of late from T4 (and those of my son's partner too yesterday) is simply avoid the bloody place and use T3 or go from another airport.
I used the hell hole last month and I had to go the ticket desk (queue) to sort out a mess on my booking and then use the check in queue and was in the line for two hours. When I had the nerve to complain about the handful of check in desks that were in use, I was told that I should have checked in on-line. I am therefore reluctant to use T4 and in future am going to be flying with AF out of T2, VS out of T3 or drive over to BRS or BHX.