Interesting that the “BD95” preset uses only the second filter. My BD sound was using a combination of both. I wonder if the first filter is more needy in terms of the harmonics it needs to excite it into self-oscillation?

Back to my first bass drum… as it happens, I did have OSC drift on but switching it off didn’t change things. I just scrapped my sound and used BD95 as a starting point to get to the more click-boom sound I was after.