Only a suggestion that I mentioned earlier. A 1/4 thick steel plate ,the width of door opening and length that goes back from opening at least a foot or more . Shim it down to be flat on concrete and will have to be bolted to plate with bolts to come up from bottom of steel plate through 2/4 plate. You would need four bolts per side to keep plate from swinging. Two bolts on end of plate and two bolts close to door opening stud. Use carriage bolts with round head and could countersink some also. You would have to remove whole panel to install steel plate. This would tie the opening width and keep whole panel in line when opening. Also there would only be 1/4 inch of plate across bottom which would be easy to roll a jack or cart and would not trip over it. Yes it would scoot on concrete when opening whole panel ,but would actually support it also.