Before I answer your other questions, let me first ask you: does your OpenSprinkler have a microSD card installed? Logging requires a microSD card. Without the card, logging should return no data. If you are not sure, check the LCD screen to see if there is a microSD icon (see page 4 of user manual https://opensprinkler.freshdesk.com/solution/categories/5000022938/folders/5000099564/articles/5000403746-opensprinkler-user-manual-firmware-2-1-0-)
Then, my next question is: is the issue repeatable? Does it still persist, or is it a one-time thing?