Garbled characters on function gen display

[royalmp2001]

HI everyone,
I bought a cheap new function generator recently on Amazon, and I notice from time to time, the LCD displays throws up garbled or corrupted characters.
I do not have the option to return this, so does anyone have suggestions how I could fix this?
I have already opened it up and unplugged and replugged all the pcb connectors.
Could it need some filtering from spurious interference somewhere, such as adding ferrite beads or something, or use a mains filter, or bigger smoothing electrolytics on the power supply board?
Any suggestions welcome.
Thanks