Thanks guys! I didn't think it would hurt, but I thought perhaps it was a question that should be posed as I couldn't find reference to it with a search. It's a bit like the question "Can you add too much water conditioner?" that came up regularly when I ran Fishkeeping groups, obvious to veterans, but something beginners wonder about.
Of course it came to mind because of a mishap due to being a beginner (surely the 10 beers had nothing to do with it!). The Airlock that came with the fermenter has no fill lines so I just put a centimetre of sanitiser in it (mixed). There was no activity by the end of the next day, so I added the other half of the 5g pack of AB-1. The day after that the Airlock was clacking away madly. I thought "no wonder Brian from the CSB YT channel doesn't like them" and tried to put up with it. After about 10 beers and a few hours of poker it was driving me nuts clacking away so I put more sanitiser in it. I tried to skim through videos to see how full they should be but I really couldn't see so I just pored some in, a bit more than I intended, the inner bit was poking out a bit, but I just pushed it down with the cap and got back to the computer in time for the next hand, with no noise from the Airlock. When I looked at it again the fluid level was only about halfway although the inside bit was still touching the lid, I assumed that it must have gone into the fermenter as it hadn't overflowed. The bubbling had stopped completely. There was no bubbling all the next day although I gently swirled it a couple of times, so at the end of the day I swirled and rocked it vigorously and bubbles came out for a while then nothing for a couple of hours so I opened the lid, pitched another 5g AB-1 and stirred it in, scraping the bottom. I realised that the inner cup like bit of the Airlock was almost full of sanitiser water so maybe not as much went in as I'd imagined, but bubbles had come out earlier that should have pushed that out I would have thought, so perhaps back pressure sucked it back in, or the bubbles didn't push it out in the first place. It's been bubbling regularly all day today, with the inner cup bouncing up and down with each bubble released. Is it possible that it had still been fermenting but because of the water in the cup and the cup not being able to rise I just wasn't getting bubbles being released? Perhaps to do with the nature of CO2?