@harmandeep.dhillon - What version of Toad are you on?
17.1 introduced an issue when scaling is set to something above 100% and if the default font size has been changed. The default Editor font is Consolas 10pt and in that setting and 125% scaling, for example, all is fine. If the font size is changed to 8pt, 12pt, 14pt, and anything else that is not a multiple of 10 then problems can appear. The issues may be that characters are painted together making them looked stacked and other issues with text jumping around especially when making a selection.
For the issues I've described, changing the High DPI settings for Toad.exe resolves them on my machine. I have sent the workaround on to another customer having these issues and I'm awaiting confirmation. You can try these on your machine and see if things are resolved. Please let me know how it turns out.
Thanks,
Michael
Note: If the change above causes scaling problems, undo the scaling change and then change fonts to one of the fonts/sizes recommended here