I think these are just random differences, Stuart. There are only two tiny changes in 5.8.5, and neither would have any effect on timeouts.
I think this problem is down to the modem. After the telnet login is completed, DSLstats has a 15 second timeout, just to avoid hanging when the modem completely fails to respond at some stage during the data collection. The timeouts you are seeing are occurring during this period. My opinion is that if the modem hasn't responded in 15 seconds then something is very wrong, and I can't think of anything more I can do to deal with it.