few things can cause it; most likely one is that the bit slipped up a bit in the collet on the initial plunge (giving you a small Z offset).
a less likely cause could be if the top of your V bit broke off somehow, but a quick visual inspection should rule that out… you can see easily if it’s sharp point or not
I don’t know what feed/speed you used and what max depth of cut for the V bit. in theory a too deep depth-of=cut could cause a missed step in the system somehow but… again less likely than the bit slipping
oh and once I had a hard case… it had turned out that my router had worked itself up a little bit in the holder and i had to retighten those holding bolts
I’ve also had the bristels of my dust shoe causing the Z not to push down as much; that caused some weird shallower cuts
btw it’s hard to know if the V bit cut too high, or if the flat bit cut too deep 