The delay is about 1 (one) second, invariably just about 1 second, and this is true on all ranges, from 1 ms/div to 10 ns/div.
The scope's working perfectly, refreshing the display at an 50Hz forced refresh rate, but when lifting the probe from the test point, the scope's freezing for 1 second with the last signal on the screen. Then it resets to 0.
As nctnico pointed out, it seems to be trigger related, as this is true only when the scope's managing to trigger.
And I don't know how to look at it... a feature or a glitch... Well I'll get used with it.
But now the firmware question remains... Did somebody managed to disassemble/modify/improve the software itself?
Thanks!