Hi, john!
Actually all the bugs in page loading do have the same nature: the old engine non-supporting ECMAscript 6 standard (latest javascript version) in full.
You can freely transfer your logins into PaleMoon (NewMoon, MyPal) or Basilisk (Centaury, Vasilisque) or any other UXP-based browser: Borealis, IceapeUXP etc.
First you can try to simply copy files key4.db and logins.json from y
Forum:
K-Meleon on Goanna