Regarding the qt wallet, it seems to take a crap load of time to both quit and to start. Last time I tried to shut down the miner I gave up after 15 minutes and forced closed it. It always takes about 4-5 minutes to start though (SSD, i5-6600K, 16GB RAM).
Ensure that none of your farms are mining to this wallet/address at the moment of closure, working miner somewhere won't let wallet close properly. Closure isn't a task, it usually takes 2-3 sec, but start is a bit slow, 3-4 min, very low cpu usage.