HPS140 handheld scope fault with 50mV or below

I have a HPS140 handheld scope it works very well as long as the input voltage is above 50mV, if it drops below the trace goes of the bottom of the scale.
In manual the trace is good and works well as long as 0.1V or above are selected if it is set to 50mV or below the trace drops of the bottom, I have moved the y position as high as it will go to no effect, if I set the i/p on the menu to GND it returns to the correct position, back to AC or DC i/p and you can see it move down the screen and off the bottom, shorting the probe or the o/p plug together does not correct the fault. Not sure when it started to do this as most of the reading I have required have been above 100mV. Interested in your reply puzzles me.
Turnbull

Looks like there is a problem with the input amplifier.
This can have different causes.
If it is caused by a manufacturing error, it will be fixed for free.
Sorry, if the problem is caused by an overvoltage at the input, you will be charged for the repair.
Please return the unit for inspection/repair to:

Velleman Projects Tech. Dept.
Legen Heirweg 33
9890 Gavere
Belgium

Make sure to include proof of purchase to qualify for repair under warranty conditions.

Thank you for the quick reply
Don’t think it was over voltage can’t think of any times I have used it on any thing over 24v.
I will send it back and we will find out.
Thanks again T

Repaired with a new one, excellent service and after sales, thank you.