Peak LH then low within hours

[fairgame84]

I've been tracking LH since we started ttc #3 in July. DH has low sperm count so we try and target certain days to dtd.
Today I got peak at around 10am but I've just tested again at 4pm and it's low.
I've never had this happen before, it's always stayed peak for a day then dropped to high the next day then low.
I used LH tests with #2 in 2021 and never had this then either.
Does anybody know what this means?

Yes peak can be very short lived (like 12 hours or less).
also you could have peaked overnight but not known it as no one tests then.