I think it is just an increase in demand on the site, year on year parkrun has been getting bigger, and given how good the weather has been recently, there have been many first timers who have increased the demand on the site.
To the runner above enquiring about your time and position, normally the system is fairly seamless, for example at Bushy Park on Saturday we had 672 runners, and managed to cope, just!
Your time is related to your position token given to you after the finish, and these are given in the order of the finishers so normally there is no confusion. The timekeeper at the finish line records all the finishing times, and these times correspond to the finishing positions. Normally there's no mix up, but if you think there was you should e-mail Leedsoffice@parkrun.com.