Nothing has changed in recent versions of DSLstats which would explain this. The Telnet Data --> Connection Stats information is the unprocessed data directly from the modem, and the way it's collected hasn't changed.
I presume other items such as SNR Margin still change by small amounts? If so, the data collection is working normally, and there's no reason for a single item within that data to get stuck.
Since G.INP was applied I notice that my attainable values hardly change at all, so I wonder if you're seeing some coincidental result of when you happened to restart DSLstats?