Cannot reproduce the JPG export delay (as I mentioned in the post this seems intermittent). I have attached a video of the blend mode pause but unfortunately this doesn't actually capture the "wheel of death", just the mouse frozen at the last screen update location. Included a time code displayed so you can see the pause starts around 00:00:08.23 and finishes around 00:00:18.33 - therefore lasting 10+ seconds. Hope this is helpful.
Will try to re-create the JPG export issue but this is dependent on whether it happens.
Blend Range Issue Video.m4v
UK-Dave got a reaction from SPaceBar in Occasional "wheel of death" appears