The Server and relays have a static cache size. It can be increased, which may help. However, the cache is first in first out. As other things get downloaded into the cache anything else that’s not being used as often will eventually be pushed out.
As an alternative we created a directory that we place all the new java updated exe’s saved as the sha-1 name and have a task manager job that checks if they already exist in the wwwrootbes directory every 10 min and if not copies it over from the directory we created.
Both ways have their pros and cons, but at least this way you don’t have to edit every Java update fixlet.