Connection settings gets altered when router power gets disrupted

I have this TP Link Router, it is the EX511 | AX3000 Dual Band WiFi 6 Router. I connects to an ONT which in turn connects to the Fibre. The ISP I make use of has its connection type as DHCP (Dynamic IP). Everything works perfectly, until the power goes off and comes back on again. Then, for some reason the connection settings reset to PPPoE, with credentials that I never entered (not malicious credentials, simply 'guest' credentials for my ISP, but still, I never entered it), and the network does not work until I manually reconfigure everything again. The only setting that gets altered is the

Question by simply_a_student on Super User, licensed CC BY-SA. We show a short excerpt and link to the original thread as credit.