I do a lot of fishing in Minecraft. Partly for EXP (slowest method of EXP gain ever, but since you people broke every other kind of EXP grinder known to gamerkind there aren't many options available) and partly because I get better enchanted books from fishing than from the enchantment table. One thing I run into now and again are items that have curse of vanishing on them. These I keep in a separate box from the other enchanted stuff I fish up.
When I synced my world to the Glitchy Together edition (and recently re-synced to get the fix for horses) I had three fishing rods and an enchanted book in a chest. One of the rods had Lure II as well as curse of vanishing, but everything else just had curse of vanishing on them.
After syncing my world, I looked in the box and I found that the rod with two enchants now only has Lure II. The other two rods and the book still have the purple shine of an enchanted item, but nothing on them. The curse of vanishing has apparently vanished itself. Was that supposed to happen?
Also, since syncing my world, I have not found or caught a single item with curse of vanishing on it, and I've fished up almost two double chests of assorted bows, rods, and books.
Thank you for your report!
However, this issue works as intended.
Curse of Binding, Curse of Vanishing, and Sweeping Edge enchantments have not yet been implemented in the Bedrock version. I assume you obtained these books in the Console Edition, which did implement them. When you transferred the world to Bedrock, those enchantments would have been deleted.