I work on strange characters insertions into code, but cause it isn't possible to simulate it, it's hard to find what is the reason.
If it happen to you, please give me information like: used highlighter file placement local of FTP or... I suspect that is caused by matching brackets code. If you can switch it off for a while in Program settings / Editor 1 - Highlight matching brackets option and report me if it happen when the code is off -- <https://forum.pspad.com/read.php?2,75694,75694> PSPad freeware editor https://www.pspad.com