Just to confirm I have same issue with my Cisco 897VA with both of the following iOS versions, unless this bug is triggered by date and time, the bug must have been around for a long time as I've tried both of the following iOSes, one is approximately 2 years old and it still has the same issue/bug.
c800-universalk9-mz.SPA.156-3.M6a.bin
c800-universalk9-mz.SPA.157-3.M3.bin
Its seems the issue is indeed caused by SNMP monitoring/polling (LibreNMS in my case... was using a C867VAE without issue before) as you'll see errors the like following after sometime (hours).
%SNMP-3-INPUT_QFULL_ERR: Packet dropped due to input queue full
That said "show controller vdsl 0" seems to stop working in minutes after said poll(ing).
