For those who use multiple instances of Sigil at once on Windows and had issues with Preview slowdowns, please give the following test build a try.
Sigil-Test-AdaptCacheOnFirstInstance-Windows-x64-Setup.exe
It is Sigil 2.7.0 but adapted to test if it is the first instance of Sigil actually running or a later instance. If the first, it nicely uses the normal Disk Caches and will remember things. If it is the second or later, it will use OFF-THE-RECORD caching that should not have problems or interfere with the first instances disk caches - BUT this needs to be tested.
You can download that build from my personal repo which can be found here:
https://github.com/kevinhendricks/Bu...nMac/releases/
If it fixes your issue with multiple instances of Sigil on Windows, feel free to keep using it as it official 2.7.0 with some extras added.