I recently used my laptop after a week and did an update. I was surprised it took 20 minutes. I have a slow connection but get continuous1MBps from W10 updates and downloading the latest ZA. This fits with Speedtest of 9.39 Mbps. But these security updates never get above 50KBps. Perhaps the W10 updates and ZA download of a new version have been cached on my IP's server to cut down their costs from their connection to the US and these are not. Perhaps they come fron the Cloud. Is it conjestion on your server? The updates show as many isolated bursts of download on Glasswire.
Thanks,
Ron