I did get something similar after installation of one test patch during last few months.
It happened each time I started LFS. As I had this same problem couple of times before, I thought it will be good idea to make a complete backup of LFS.
Deleted cfg.txt in original LFS and problem magically disappeared, thing is it also disappeared in backup
As I don't have exact way to reproduce it I didn't want to write anything...
I earlier reported also something similar :
https://www.lfsforum.net/showthread.php?t=83195
I guess if resolution change fail, you shouldn't be constantly retry it, but revert to previous state
And as I started to write about this bugs, one more totaly random, absolutely have no clue about its cause or anything...
Sometimes (very rarely) when I start LFS in full screen, it doesn't accept any keypresses and other windows flicker like each second. I guess other window receive key messages...
AFAIK that happen only when there it that LFS intro (FBM@BL1 replay), but when it reaches entry screen everything is fine.
Could that be this same bug? :
https://www.lfsforum.net/showthread.php?t=65750