SpinalSim: onSamplings can't work properly with clock from a blackbox

Spinal version: v1.10.1
Simulation tool: Synopsys VCS 2018

Here's the simulation code:

        SimTimeout(500 ms)
        val perpPort = dut.socInst.logicMainInst.coreInst.io.d_perp
        val coreCd = ClockDomain(dut.socInst.logicMainInst.smuInst.io.coreClkRst.clk)
        InitBase.doInit(dut, 10 MHz, "00".asBin)
        infoMonitor(perpPort, coreCd)
        var numCnt = 0
        coreCd.onSamplings{
            if(perpPort.aw.valid.toBoolean && perpPort.aw.addr.toBigInt == 0x30006040L){
                val data = (perpPort.w.data.toBigInt & 0x000000FF).toChar
                println("state of ready: " + perpPort.aw.ready.toBoolean + " , count = " + numCnt + " , char is " + data)
                numCnt = 0
            }else{
                numCnt += 1
            }
        }
        sleep(100 ms)
        simSuccess()

All the signals here are set with "simPublic".

I want to record the cycles between two transport, but it gives me such a callback:

state of ready: true , count = 3125 , char is S
state of ready: true , count = 8 , char is M
state of ready: false , count = 6 , char is U
state of ready: false , count = 6 , char is  
state of ready: true , count = 14 , char is n
state of ready: false , count = 6 , char is i
state of ready: false , count = 6 , char is t
state of ready: true , count = 14 , char is S
state of ready: false , count = 6 , char is u
state of ready: false , count = 6 , char is c
state of ready: true , count = 14 , char is e
state of ready: false , count = 6 , char is s
state of ready: false , count = 6 , char is s

And the wave is:

Well, it's extremely unexpected... The number of count is obviously wrong, and the char "I" is missing.

The only special is the clock is from a simulation model of an RC osc.

So is there anything wrong about this? Maybe I need to offer a simplified model?

Start by reducing the provided SpinalSim example around ClockDomain.onSamplings, the blackbox-derived clock, and the simPublic signals, then reproduce it with Synopsys VCS 2018. Compare callback counts and captured characters with the waveform; done means the behavior is explained and the issue has a reproducible fix or documented limitation.