I’m having the same issue, and it’s really annoying as my world depends on custom blocks to function properly!!
I have discovered that if you remove the minecraft:destroy_time minecraft:loot minecraft:explosion_resistance and pretty much all other components except minecraft:flammable, it kinda fix the issue and the block appears in the world (useless without any components)
Still not fixed my world is litterally unplayable unless i remove my addon which is frustrating because everything is built around it
It is not an issue with the addon though because it does work in other worlds and removing the blocks folder does make it work so i concluded that it is a problem with blockshape of existing blocks!!
I thought that it was because of an error in my addon but then i tried other addons and the same thing kept happening like if there was a limit for added items
For example if i put multiple addons together adding more than 120 items the extra items are overriden by the last one alphabetically
You need to install the Vanilla Music Pack from the marketplace to hear jukeboxes and other music related sound effects