[KevinH]

The problem is that code is identical across platforms, and I am not seeing any of this on macOS but did see and was able to fix those issues when reported for Sigil-1.6.0.

But with Sigil-1.7 on macOS, I am just not seeing what you are seeing.

Here is a screen cap following your instructions after editing a line to add the word "Hello" to the start of the line and waiting for Preview to reload.

As you can see it is syncing just fine.

I also try with Go-To-Link-Or-Style on red and then back and it all worked just fine.

So this is going to be very hard for me track down on macOS as I can not recreate it.

Let's hope someone (Doitsu, BeckyEbook, DiapDealer, etc) using Sigil-1.7.0 can recreate what you are seeing on Linux or Windows. If not, I can try and create a debug build for you that adds a bunch of QDebug() output related to Preview position that you can capture in a debug log file so we see what is going on.