I don't remember if 1.2.1 (and I'm too tired to check this out) does download the full history, but in B3 1.2.2b there is a limitation that prevents the bot from downloading more than 20kB of data from your game log file tail.
This has two consequences :
* at bot start, at most 20 kB of history will be downloaded
* let say you had network issues for a few minutes and more than 20kB of data were added to the game log, then B3 will loose a bit of what happened in the mean time.
I would try out 1.2.2 beta just to be sure
