R plot shows uncommon hex like numbers on axis

Question

I couldn't find an answer for this very easy question, because I don't know how to describe or even name the question. The code is extremly simple but it happens everytime I use the "plot" function in my jupyter notebook.

    n  <- 10
alpha  <-  rnorm(n,60,10)
beta  <-  rnorm(n,0,10)

Hbar  <-  150
Hseq <- seq(from=130,to=170,len=30)
plot(NULL,xlim=c(130,170),ylim=c(10,100),xlab="height (cm)", ylab="weight (kg)")
for (i in 1:n)
    lines(Hseq, alpha[i] + beta[i] * (Hseq-Hbar),
         lwd=3, col=sample(1:10, 1))

The result looks like this:

For sure the axis should show "numeric numbers" instead of these "hex!?" onces. I think it have something to do with my R or jupyter version so:

• Ubuntu LTS 20.4
• anaconda 4.10.3
• r-base 3.6.1
• jupyter_client 7.1.0
• jupyter_core 4.9.1
• newest firefox version

Or maybe the keycode-table? What can I do?

Could this be helpful?

Sys.getlocale()

'LC_CTYPE=C.UTF-8;LC_NUMERIC=C;LC_TIME=C;LC_COLLATE=C;LC_MONETARY=C;LC_MESSAGES=C;LC_PAPER=C;LC_NAME=C;LC_ADDRESS=C;LC_TELEPHONE=C;LC_MEASUREMENT=C;LC_IDENTIFICATION=C'

Update: After restarting the conda enviroment and the r-kernel, it works without any changes in the code or packages. Even if I tried this before, I don't get it. So the cause or solution stays unclear.