Long story short, I have gaps in my history in Firefox. I'm on the latest stable desktop version, but this happens both on Linux (Ubuntu 20.04) and Windows 10. I can't really pin down what causes this, it seems totally random. Every now and then, I'll be browsing, close the browser, realize I need to do something on a page I was recently on, I relaunch, press "ctr+h", go to the 'Today' drop down tab, and the most recent entry is multiple hours old, in some cases it's not even from the same day. The pages I was just on are nowhere to be found. I would guess it's just late to update the history, but then there are times where I'll go through my history from a few days ago looking for a specific page I know I visited, and I'm able to find some but not all. Again, it just seems like there are random gaps in my history.