Best to use wired foundation for loosening, definitely not unwired or thin, as it won’t withstand the force. This happens - see pic!
Another tip is to use older super combs that have been used a few seasons as they get stronger from general use by the bees. Again must be wired for loosening and spinning in a swing cage or tangential extractor, not a radial
What loosener are you using? I’ve tried the plastic Abelo one and it does work, but it’s messy as the plastic rods are too thick in my opinion. My old fashioned hand held one by Mountain grey which has stainless steel thin pins, is much better but you can no longer buy. Have to keep an eye out at auctions
I’ve attached a photo of a comb I loosened using the Abelo plastic loosener, as a trial which I bought for our association’s use. I simply pushed it until it hit the foundation then wiggled it a few times in the cells before moving to the adjacent piece of comb. It’s time consuming but the comb stays intact during spinning and it spun out well and bees will repair the cell walls.
I’m concluding I’ll use this method for heather blended by the bees with balsam / wildflowers but I will scrape comb for pure heather and do cut comb. Life is too short! Again need a strong wired midrib or plastic foundation if scraping back if you want to keep some of the comb, otherwise use thin and cut the lot out and start again next season
Hope this helps
Elaine