Hi Marc,
Here is a clue. In Firebug (network panel), compare the GET command that
is sent when everything is alright, with the other GET command where there are delays. The parameters of the GET command where delays happen, are weird (I see an underscore as one of the parameters).
As a result, when all is fine, most GET commands are replied with a "304 not modified" and served by the cache, whereas the weird parameter causes a not cacheable request (replied by "200 OK").
Try to find where this underscore as a GET parameter comes from.
I fixed the issue and committed to the repo. I think now this feature works correctly and sorry for the delay. I'll start working with my 4th task tomorrow. Thank you.
Regards, Thilanka.