When the loops are damaged, it is worth looking into the reason. It could be there is some roughness on the nocks of the limb tips.If there is, it could damage the repaired loops or a new string.When I had that problem I used a shoe lace and rubbed some polishing compound into it. Then rub the limb nocks with the lace, in the same sort of action you use to clean spokes on a bike.( the sawing sort of action; not rubbing up and down the spoke)
If the bowstring under the serving isn't damaged, I would just serve over the old stuff, by hand as there is no room for a jig.You will have two ends to tie off. I would arrange the ends so they are where the loop enters the end serving.Cross the ends over each other a couple of times, going round the bow string, and tie a neat knot.Make sure the knot stays facing you when the string is on the bow, so it doesn't press into the limb.This may be a temporary repair or longer lasting. However, if you keep an eye on it you will find out if the limb tips are still causing damage to the loops; and you won't have used another new string to find out.