Charts not refreshed in ClassicUI

I discovered that my charts are not refreshed with recent data in Classic UI. I am using RRD4J as persistence.
I first thought it was a bug in OH 2 but I finally discovered that I have exactly the same behaviour in OH 1.8 !

As soon as I clear my WEB browser (Firefox) cache (with Ctrl+F5), charts are then displayed with recent data.
If I do not clear the cache, charts never displayed new data.

Is it a known bug ?

My persistence conf file:

// persistence strategies have a name and a definition and are referred to in the "Items" section
Strategies {
    // for rrd charts, we need a cron strategy
    everyMinute : "0 * * * * ?"

Items {
    GTemperature*, GHumidite* : strategy = everyChange, everyMinute, restoreOnStartup
    GVirtualData* : strategy = everyChange, restoreOnStartup

And a part of my sitemap:

`            Switch item=TempChart1Periode mappings=[0="4 heures", 1="12 heures", 2="Jour", 3="Semaine"]
            Chart item=GTemperatureInt period=4h refresh=5000 visibility=[TempChart1Periode==0, TempChart1Periode=="Uninitialized"]
            Chart item=GTemperatureInt period=12h refresh=10000 visibility=[TempChart1Periode==1]
            Chart item=GTemperatureInt period=D refresh=30000 visibility=[TempChart1Periode==2]
            Chart item=GTemperatureInt period=W refresh=30000 visibility=[TempChart1Periode==3]

An issue iwas already opened:

And a PR is proposed waiting for an approval.
Wait and see.