Some times Safari on Mac OS has problems with fetching files from tlwebaccess. This seems to happen after a ThinLinc upgrade most of the time.
Could be related to bug 5711.
Does not only happen after a ThinLinc server upgrade.
Easily provoked by disabling the cache in Safari.
Looking at the stats it seems like the entire file gets transferred. So a guess is that we do not shut down the TLS session properly, instead just closing the TCP socket. Or failing to flush the last few bytes.
Also see bug 7392 which is also about issues loading files.
We can no longer reproduce this problem, even with ThinLinc 4.8.1. Tested on macOS 10.14 and Safari 13.