I have just discovered a timing issue (self inflicted ) that you may run into also ,
and may not realize what has happened .

Flashing firmware using the Arduino Ide the cpu frequency for the esp8266 is 80MHz.
I think most will set this to 160MHz but it can be overlooked and if so issues will arise especially if boards were updated or esp's were programmed months apart etc.

I have been installing various firmwares on multiple esp8266 -01's for different pixel types
of which one is using ws 2801 pixels @ 80MHz not realizing/recollecting that the others were @160MHz for ws 281* pixels . For the life of me I could not understand why the the sequences on the ws 2801 always seemed to be delayed .

Then I woke up the the cpu setting .

Just an fyi if you may suffer this issue .