Their web site used to be consistently bad this way... I think it was running on a Windows server... anyway they have revamped it and I generally don't have problems with it anymore. But it's worth trying again or calling them; as far as I'm concerned they've been great to do business with!
The last couple of times I have used them their site has been a bit wonky. But they are very easy to get in touch with, you go straight to a human being, etc. Only good experiences with KEH.
Yesterday it was messed up, but at the moment it seems to be happily purring along. There were some Internet attacks yesterday (NYTimes) maybe there's a digital conspiracy against film cameras!
For a while now I've only been able to bring up the first page of search results. If I get 40 of 43 for example, I have to be content because I'm never going to see those last 3.
With respect to search results on their site, just browse their inventory with the item count set to "All". Everything should load up. The site does run slowly at times.