After a great deal of trouble getting this transferred over, I think I found what was giving me trouble. First, clearing the formatting for the posts I was copying/pasting helped. I could not publish anything that had incompatible formatting. I recommend going to the 3 dots at the top right and clicking the T with an x in the lower right corner to clear formatting. It's pretty easy to do, and you can do it with a large clump of text if you highlight it.
The second issue is something I can't find a work around. Spoilers come with a "title" and after entering a title, I figured out why text was getting overwrriten when I added text or pictures. The spoilers appear to be broken in multiple different ways. If I add a spoiler, I can't update the post with pictures. If I add multiple spoilers, the text in spoilers that come next will randomly get overwritten with content from another spoiler above. I can't even highlight a section to add spoilers for a portion of the post. While the spoilers are acting up, I won't add spoilers to this topic. I apologize for any inconvenience this causes loading the thread.