My workflow:
1. Set up a mastering signal path in the "Plugin Chain", and tweak plugins until I'm happy.
2. Use "Save As..." to save the file to FLAC, which applies the processing chain.
3. The progress bar on the save usually gets to about 2/3rds then Sound Forge is unresponsive for as long as a minute.
I record to WAV, but save mastered files to FLAC, and then to MP3 for streaming. Saving to FLAC & MP3 both exhibit the long freeze at the end of rendering.
It appears - if I check in Windows Explorer - that when Sound Forge is unresponsive, the saved file has already been finished and closed.
So Sound Forge is doing SOMETHING for a long time, after it gets done, but I'm not sure what it is, and I wish it did less of it.
This gets better - for a while - if I use "File->Reset all preferences and cached data" - but if I do that I lose whatever changes I've made to preferences.