windows 10 pro 64 bit 2004 comp. 19041.388
KPM 126.96.36.19976 (k) / 1593510272_6509 / 1.0.363.0-0.8.3.0_1 (Firefox extension installed)
Firefox 79.0 64 bit (Lockwise disabled, AdBlock Plus, KPM and KP enabled)
My KPM suddenly stopped autofilling login and password for some sites and for other fills only password or only login. After deleting the entry in KPM for this problematic pages KPM does not prompt for saving the login and password.