As far as I can, there is no persistent storage of the statistics on the box. For example the following command "/etc/init.d/dsl_control status" will query the dsl driver for the statistics. And more over each side of the connection is responsible for its own "half" of the statistics; only the dslam/msan knows about upstream errors, so the modem needs to query these values over the dsl link; but that also means that the dslam/msan is responsible to reset them. And I guess the dslam will have its own rules about resetting, a simple re-train of the dsl link might not be sufficient. So are both near and far values in your statistic impervious to rebooting the modem, and what about keeping the modem powered-down for say 15 minutes does that have an effect?
But I just got curius and it sees if you use the following command sequence on your router (via the command line interface):
. /lib/functions/lantiq_dsl.sh ; dsl_cmd pmr 0
. /lib/functions/lantiq_dsl.sh ; dsl_cmd pmr 1
. /lib/functions/lantiq_dsl.sh ; dsl_cmd pmr 2
. /lib/functions/lantiq_dsl.sh ; dsl_cmd pmr 3
. /lib/functions/lantiq_dsl.sh ; dsl_cmd pmr 4
. /lib/functions/lantiq_dsl.sh ; dsl_cmd pmr 5
That reset all counters on my lantiq vr9 based homehub 5A. The command pmr is short for "PM_Reset"; in my case parameters 0 to 5 gave a "nReturn=0 " output, 6 and above did not. Since I issued those commands the error counters have not yet started to climb up from 0, so the command might not do what I think it does, but technically, even if the counters will remain at 0, it should be a valid answer to the question how to reset the counters... Okay, at least some of the counters started to show values > 0 again, so I believe the above does what you want...