Amount textbox goes blank when bigger number entered

When I enter amount bigger then 1000, the textbox goes blank when I leave it. It still contains the correct amount.
Unable to replicate on https://demo.globalqss.com/webui/ so far.
The two screenshots shows the amount entered and what happens when I press TAB.

This happens not only on the GL Journal, but everywhere where an amount is about to be inserted.
I assume it may be regional settings related somehow; my UI language is Engilish.

Request sent to http://localhost:8081/webui/zkau looks like:

cmd_0 onChange
data_0 {"value":"1000","start":null}
dtid z_f5_0
uuid_0 rQgUno2