I can't reproduce those lags with my webserver.
This might be your webserver caching the log file or something similar as you said that it works flowlessly with FTP (even if not shown in the provided log file)
I might add that the B3 server I am using is also running several BO beta bots (which use the HTTP obviously) without any issue.
I will pass this on to the GSP although it seems odd that when i manually download the log it is updated everytime.
Thanks