Hi @Elco and @Bob_Steers,
Just writing to send feedback about latest firmware. On my Spark 2, the screen used to be just solid white (for several years at least) and now shows the expected blocks!
I updated firmware from 2020/10/29 
2020/12/02.
This was completely unexpected but I’m pleased! Kudos!
I’m not entirely sure why that’d be fixed now, but good to hear it magically started working again =)
Yep, strange but pleased. Just to add more details, it used to work very infrequently, no more than about one time in 10. However, since the latest flash, it’s worked consistently for 5 power cycles. That’s significant enough for me to call it fixed. I’ll post a follow-up if it fails to display blocks again.
It could also very well be a wonky connection in the display ribbon. If it’s firmware, irregular occurrences make it sound like a timing issue - the bug would still be there, but is “fixed” because something in the firmware is just a little bit faster or slower than it was before.