FL that first had FLEX I think, if not that one then a recentish one. What happens is that when a song is saved as a new file (not saved to an existing file) focus is lost on the fl ...
FLStudio Asio or the ASIO4ALL it doesn´t happen.
On a side note the FLStudio Asio gives me about 80ms overall latency even on an empty template vs 30+ms from the Focusrite USB ASO and the ASIO4ALL ...