historical HP-41C display fault

[ColinJDenman]

A recent thread about the oldest 41 jogged my memory about my early experience with mine and I wonder if it was a common problem back then,

After a few months of ownership, my LCD began to blacken in the top left corner, eventually obscuring the top and left bars of the first digit. As it was still in warranty and getting worse over time I sent it back to the supplier for fixing.

As my first HP, I treated it like the crown jewels, so it definitely didn't get any knocks, drops or other rough handling. So I'm curious, was it a one-off, a fault others recognise, or what?