The cause: The data advertised in the HTTP Headers and the data delivered over the wire are clearly out of sync, which is the cause of this issue.

Solution:

A Solution for the error net err_content_length_mismatch:

Expand the cache’s capacity. Some files cannot fully load because of the tiny size of the nginx proxy cache area by default. You can configure nginx to change the nginx cache area for a standard jQuery framework.

http{
................................
proxy_buffer_size 128k;
proxy_buffers 32 128k;
proxy_busy_buffers_size 128k;
.............................
}