Described the problem here:
PaperMC/Velocity#1624
Maybe, if it can't be fixed, you'll add API to say FastMOTD take value which was set via FastMOTD API?
Also, btw, you have some small bottleneck:
Don't do any math operations if value is constant. Do it only for dynamic values.
You have + * + / on each ping, it's strongly bad ☠️
Also update your benchmarks after fixing this one ^
And find similar redundant excessive calculations