ppp lost part of account ID resulting in failed authentication

Kit = hAP AC2 on 6.49.3 packages and firmware. ISP is VDSL2 via a modem. Simple domestic setting (ppp, wired ethernet, wireless, IP4). Mostly managed through Winbox, but comfortable with CLI

The last four characters of my user name on Dial Out pppoe on Eth1 went missing. has anyone else experienced this? Sometime between midnight and 05:23 UTC (oldest surviving log). As a result, the connection would not authenticate. I added the last four characters back in and it immediately authenticated. Unfortunately all I’ve got in the logs is 5000 lines of pppoe disconnecting, initializing, connecting, terminating every 10 seconds.

I know that there was planned maintenance on a broad range of exchange numbers including mine (between 00:00 and 00:60). But I can’t see how this would cause this problem. There are no other changes to the hAP. If it was a hack attempt, what would an attacker gain from this? It seems more like a fault. The only finger trouble I can imagine is that last time I looked at the ppp settings I accidently deleted some of the login name and it only became apparent when the hAP had to reauthenticate overnight.

Anyone else seen this?

Thanks!