BNC to VGA converter flickering

[Tomeeii 0]

Hi

 

I would like replace my old 1995 CNC machine old CRT (single green color) monitor to flat VGA.

I bought one BNC to VGA adapter and looks working but image randomly juming little bit.

here is one video about problem:

 

any idea how can i get them out that noise?

 

monitor on screen say its 1280x1024 x75hz the resouliton.

 

Thanks Tom