
How much available built-in storage do you have? If it's almost full, here's a link that'll help to clear some storage: How to free up storage space on your Mac.How big were those files, and how many photos did they include? You also mentioned you've been able to export a slideshow to an m4v file in the past.You mentioned running First Aid from Disk Utility, but please confirm if any errors were found/fixed.What occurs if you try exporting a slideshow of say, 20 photos? Please keep us posted on the results. As you're dealing with a lot of photos all at once, this could be expected behavior.We'd like to help however we can, but you may need to contact Apple Support and their Photos experts. Is this just a Big Sur problem? Help please!

then reduced the library with the recently created slideshow to just the photos and the slideshow concerned - size 21.33 GB, and placed on XHD - attempted export > crashed, "out of memory".split the library into 3, of about 140 GB each- attempted export > crashed, "out of memory".shut down all other apps so that only photos and activity monitor open when trying to export the slide show- attempted export > crashed, "out of memory".original library size was 450 GB (about 100,000 photos) - attempted export > crashed, "out of memory".In summary, I have tried the following steps, with the same result each time - app crashes, "out of memory sgn comes up." After each step I used the repair function on photos app, and also first aid on disk utilities. The current size of the photoslibrary file is 21,33 GB. This failed attempt is the first I have tried with Big Sur 11.0.1 installed. I have never had this problem before, and I create a lot of slideshows and export them as mv4 files - ever since iPhotos was included with macos in 2002. The photos app crashes, and a sign comes up, "out of memory". My mac is MacBook Pro (15-inch, 2019) with 16 GB memory.

I am unable to export a slideshow of 837 slides as an m4v file from my photos 6 app.
